Zootaxa, A revision of the Neotropical genus

Zootaxa 2538: 1–37 (2010) www.mapress.com / zootaxa/

ISSN 1175-5326 (print edition)

Article

Copyright © 2010 · Magnolia Press

ZOOTAXA ISSN 1175-5334 (online edition)

A revision of the Neotropical genus Sacosternum Hansen (Hydrophilidae: Sphaeridiinae: Megasternini) MARTIN FIKÁČEK 1 & ANDREW E. Z. SHORT 2 1 Department of Entomology, National Museum, Kunratice 1, CZ-148 00 Praha 4, Czech Republic, and Department of Zoology, Faculty of Science, Charles University in Prague, Viničná 7, CZ-128 44 Praha 2, Czech Republic. E-mail: [email protected] 2 Division of Entomology, Biodiversity Institute, University of Kansas, Lawrence, KS, 66045 USA, and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA. E-mail: [email protected]

Table of contents Abstract ............................................................................................................................................................................... 2 Resumen .............................................................................................................................................................................. 2 Introduction ......................................................................................................................................................................... 2 Material and methods .......................................................................................................................................................... 3 List of species ...................................................................................................................................................................... 3 Key to known species of Sacosternum ................................................................................................................................ 4 Taxonomy ............................................................................................................................................................................ 5 Genus Sacosternum Hansen, 1989 ...................................................................................................................................... 5 Species descriptions ............................................................................................................................................................ 8 Sacosternum auribleps sp. n........................................................................................................................................ 8 Sacosternum cruciphallus sp. n. .................................................................................................................................. 9 Sacosternum delta sp. n. ............................................................................................................................................ 12 Sacosternum emissarium sp. n. ................................................................................................................................. 13 Sacosternum epulum sp. n. ........................................................................................................................................ 15 Sacosternum garciai sp. n. ........................................................................................................................................ 16 Sacosternum inconnivum sp. n. ................................................................................................................................. 19 Sacosternum lebbinorum sp. n. ................................................................................................................................. 24 Sacosternum megalopus Hansen, 1989 ..................................................................................................................... 25 Sacosternum sp. A ..................................................................................................................................................... 28 Sacosternum sp. B ...................................................................................................................................................... 28 Unidentified material ........................................................................................................................................................ 29 Sacosternum sp. ......................................................................................................................................................... 29 Reconstruction of phylogenetic relationships ................................................................................................................... 29 Results of the analysis ....................................................................................................................................................... 34 Discussion ......................................................................................................................................................................... 35 Acknowledgements ........................................................................................................................................................... 37 References ......................................................................................................................................................................... 37 Appendix ........................................................................................................................................................................... 37

Accepted by A. Solodovnikov: 15 Jun. 2010; published: 16 Jul. 2010

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Abstract The previously monotypic genus Sacosternum Hansen, 1989 is revised and redefined. Eleven species are recognized, of which eight are described as new: Sacosternum auribleps sp. n. (Brazil), S. cruciphallus sp. n. (Panama), S. delta sp. n. (Brazil, Paraguay); S. emissarium sp. n. (Costa Rica), S. epulum sp. n. (Brazil), S. garciai sp. n. (Costa Rica, Panama, Venezuela); S. inconnivum sp. n. (Costa Rica, Panama), and S. lebbinorum sp. n. (French Guiana, Peru, Brazil). Sacosternum megalopus Hansen, 1989 is newly recorded from Costa Rica. Two species, referred to as Sacosternum sp. A (Peru) and S. sp. B (Costa Rica) are left undescribed pending on the collecting of males. Additional unidentified specimens are recorded from Mexico (Veracruz State), Guatemala, Costa Rica, Panama, and Venezuela. A key to known species of the genus is provided, important characters are illustrated. A reconstruction of the phylogenetic relationships of Sacosternum species is performed, based on 51 adult morphological characters. The genus Sacosternum is decisively resolved as monophyletic based on six unique synapomorphies. Three species (S. epulum sp. n., S. lebbinorum sp. n. and an unidentified species of the “S. cruciphallus complex”) were collected in association with ecitonine army ants of the genera Eciton and Labidius. The possible preference of the Sacosternum species for the organic-rich leaf litter below the bivouacs of these ants is hypothesized from their label data and possible morphological adaptations are discussed. Key words: Coleoptera, Hydrophilidae, Sacosternum, new species, morphology, phylogenetic analysis, association with ants, Neotropical Region

Resumen El anterior género monotípico Sacosternum Hansen, 1989 fue revisado y redefinido. Once especies fueron reconocidas, de las cuales ocho son descritas como nuevas: Sacosternum auribleps sp. n. (Brasil), S. cruciphallus, sp. n. (Panamá), S. delta sp. n. (Brasil, Paraguay); S. emissarium sp. n. (Costa Rica), S. epulum sp. n. (Brasil), S. garciai sp. n. (Costa Rica, Panamá, Venezuela); S. inconnivum sp. n. (Costa Rica, Panamá) y S. lebbinorum sp. n. (Guayana Francesa, Perú, Brasil). Sacosternum megalopus Hansen, 1989 se registra nuevamente en Costa Rica. Dos especies, Sacosternum sp. A (Peru) y S. sp. B (Costa Rica) quedan sin describir y pendiente la colecta de machos. Otros especímenes sin identificar son registrados en México (Estado de Veracruz), Guatemala, Costa Rica, Panamá y Venezuela. Se da una clave para identificar especies de este género e importantes caracteres son ilustrados. Una reconstrucción de las relaciones filogenéticas de las especies de Sacosternum fue llevada a cabo basada en 51 caracteres morfológicos de adultos. El género Sacosternum se resuelve totalmente como monofiletico basado en seis únicas sinapomorfias. Tres especies (S. epulum sp. n., S. lebbinorum sp. n. y una especie no identificada de el “complejo S. cruciphallus”) fueron colectadas junto con ecitoninos hormigas soldado del genero Eciton y Labidius. La posible preferencia de la especie Sacosternum por la hojarasca rica en compuestos orgánicos bajo los refugios de estas hormigas se da como hipótesis de los datos marcados y posibles adaptaciones morfológicas son discutidas. Palabras clave. Coleopteros, Hydrophilidae, Sacosternum, especies nuevas, morfología, análisis filogenético, asociación con hormigas, región Neotropical

Introduction The genus Sacosternum Hansen, 1989 was described to accomodate a single species, S. megalopus Hansen, known from three specimens collected in the Cordillera de Talamanca in Panama in 1979 (Hansen 1989). The separate generic status of these specimens was justified by a few characters unknown for any other representative of the tribe Megasternini, i.e. the extremely widened shield-like median portion of prosternum, extremely enlarged eyes and presence of fine longitudinal ridges on abdominal ventrites. Besides the morphological characteristics provided, no additional information was available about the habitat or collecting circumstances of the specimens. During the last few years we have inspected many institutional collections, reviewing large amounts of terrestrial hydrophilid material from Central and South America. Even though Sacosternum proved to be very rare in the collections, we succeeded in accumulating 85 additional specimens from across the Neotropics, ranging from southern Mexico to southern Brazil and Paraguay. Ten new species have been recognized within this material and the first data on collecting circumstances and their biology were gained, suggesting a possible association of the Sacosternum species with the ecitonine army ants.

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Within this paper, we summarize all available data concerning the genus along with the taxonomic revision, phylogenetic analysis and discussion about the association of the genus with army ants.

Material and methods We examined 88 specimens of the genus Sacosternum for this study. All holotypes and a portion of each paratype series were dissected. Genitalia were placed on a transparent plastic label below the beetle in watersoluble dimethyl hydantoin formaldehyde resin (DMHF), or on a small piece of glass below the beetle in a drop of Euparal soluble in 96% alcohol (in the holotype of S. megalopus and one specimen of S. garciai. Label data are cited verbatim, using a slash (/) for dividing separate rows and a double-slash (//) for dividing separate labels. Male genitalia drawings are based on the aedeagophores of the holotypes temporarily mounted in glycerine-gelatine and were prepared using a drawing tube attached to the Olympus BX-51 compound microscope. Habitus photographs were taken using Olympus Camedia C-5060 camera attached to Olympus SZX9 binocular microscope and subsequently edited in Adobe Photoshop 7.0 partly using the procedures described at Darci Kampschroeder´s website at http://www.nhm.ku.edu/illustration/. SEM micrographs of uncoated specimens were prepared at the Department of Paleontology of the National Museum in Prague using Hitachi S-3700N scanning electron microscope. Morphological terminology follows Komarek (2004) and Fikáček (2010). Sternite 8, bearing important characters, was erroneously called “tergite 8” by Fikáček & Hebauer (2009); we have realized this mistake during the preparation of this study and refer the sclerite correctly as “sternite 8”. Methodology used for the phylogenetic analysis is described in the respective chapter. Depositories CMN CNC CUIC FMNH FSCA INBio KSEM MALUZ NMPC UCDC ZMUC

Canadian Museum of Nature, Ottawa, Canada (R. Anderson); Canadian National Collection, Ottawa, Canada (A. Davies, P. Bouchard); Cornell University Insect Collection, Ithaca, U.S.A. (J. Liebherr); Field Museum of Natural History, Chicago, USA (J. Boone, M. Thayer, A. Newton); Florida State Collection, Gainesville, U.S.A. (P. Skelley); Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica (A. Solis); Natural History Museum, University of Kansas, Lawrence, U.S.A. (A. Short); Museo de Arthrópodos, Universidad del Zulia, Venezuela (J. Camacho, M. García); Department of Entomology, National Museum, Prague, Czech Republic (M. Fikáček); Bohart Museum of Entomology, University of California, Davis, U.S.A. (S. L. Heydon); Zoological Museum, University of Copenhagen, Denmark (A. Solodovnikov).

List of species S. auribleps sp. n. S. cruciphallus sp. n. S. delta sp. n. S. emissarium sp. n. S. epulum sp. n. S. garciai sp. n. S. inconnivum sp. n. S. lebbinorum sp. n. S. megalopus Hansen, 1989 Sacosternum sp. A Sacosternum sp. B REVISION OF THE GENUS SACOSTERNUM

Brazil Panama Brazil, Paraguay Costa Rica Brazil Costa Rica, Panama, Venezuela Costa Rica, Panama French Guiana, Peru, Brazil Costa Rica, Panama Peru Costa Rica Zootaxa 2538 © 2010 Magnolia Press ·

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Key to known species of Sacosternum Characters used for the identification of species largely agree with those used for the phylogenetic analysis, therefore refer to the respective chapter for their more detailed explanation. 1

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Body highly convex in lateral view (Fig. 2). Pronotum evenly convex, without sublateral impressions (Fig. 1). Preepisternal elevation of mesothorax triangular, lacking median longitudinal carina (Figs. 49, 53). Lateral portion of anterolateral ridge subparallel to posterior margin of mesocoxal cavity and bent anteriad laterally (Fig. 53). Abdominal ventrites 2–5 without distinct longitudinal ridges (Fig. 31). Head without oblique impressions between eyes. ............................................................................................................................................................................. 5 Body weakly convex in lateral view (Figs. 4, 6). Pronotum evenly convex or bearing 1 to 2 weak impressions on each side (Figs. 29, 30). Preepisternal elevation linear, narrowly suboval or arrow-head shaped with median longitudinal carina (Figs. 46–48), never in the form of a triangular plate. Lateral portion of anterolateral ridge bent posteriad laterally, therefore markedly divergent from the posterior margin of mesocoxal cavity (Figs. 50–52, 54–55). At least abdominal ventrites 1–4 bearing distinct longitudinal ridges (Figs. 32–33). Head at least with weak oblique impressions between eyes (Fig. 27). ....................................................................................................................................... 2 Lateral portion of metaventrite with a triangular area situated between anterolateral ridge and lateral margin of the metaventrite, delimited by an additional oblique ridge anteriorly (Figs. 52, 54–55). Preepisternal elevation narrowly drop-like (2.5× longer than wide; Figs. 48, 52) or arrow-head-shaped with distinct median longitudinal carina (Figs. 47, 54–55). Prosternal plate with lateral projections divided by ridges (Fig. 44). Pronotum with very weakly developed longitudinal sublateral impression on each side (sometimes distinct only posteriorly) (Fig. 29), rarely evenly convex, lacking longitudinal impressions..................................................................................................................... 3 Lateral portion metaventrite without distinct triangular area between anterolateral ridge and lateral margin of metaventrite (Figs. 50–51). Preepisternal elevation in the shape of a very narrow plate (4.0–5.5× longer than wide; Figs. 46, 50–51). Prosternal plate without lateral projections divided by ridges (Fig. 43). Pronotum usually with two well developed longitudinal impressions on each side (Fig. 30) .................................................................................. 6 Preepisternal elevation narrowly drop-like, flat or slightly concave medially, without median longitudinal carina (Figs. 48, 52). Lateral portion of anterolateral ridge continually bent posteriad (Fig. 52). Posterior margin of abdominal ventrite 4 with or without denticles. Apical sclerite of median lobe rather wide, triangular apically (Figs. 24–26). ........................................................................................................................................................S. lebbinorum sp. n. Preepisternal elevation arrow-head shaped with distinct median longitudinal carina (Figs. 47, 54–55). Lateral portion of anterolateral ridge convex to angulate before reaching lateral margin of metaventrite and therefore “zig-zag”shaped (Figs. 54–55). Posterior margin of abdominal ventrite 4 always with distinct denticles. Apical sclerite of median lobe narrow, with almost parallel lateral margins (Figs. 12, 20)..................................................................... 4 Anterolateral ridge of metaventrite indistinctly angulate (Fig. 55). Median prosternal carina slightly elevate anteriorly in lateral view.Median lobe wide apically, with sclerotized median part triangularly widening postreriad; lateral sclerites present (Figs. 19–20). Abdominal ventrite 5 entire posteriorly in both sexes................ S. inconnivum sp. n. Anterolateral ridge of metaventrite distinctly angulate (Fig. 54). Prosternal carina straight in lateral view. Median lobe rather narrow apically, only slightly widened subapically; lateral sclerites absent (Figs. 11–12). Abdominal ventrite 5 weakly emarginate posteriorly in females. .................................................................................... S. delta sp. n. Pronotum with very distinct mesh-like microsculpture. Preepisternal elevation concave. Posterior margin of all abdominal ventrites entire, without denticles. ................................................................................. Sacosternum sp. A Pronotal interstices shiny, without distinct microsculpture. Preepisternal elevation flat, its median portion not impressed. Posterior margin of all abdominal ventrites denticulate ................................................ Sacosternum sp. B Head with a small tuft of erect yellowish setae anteriorly of each eye, having the appearance of small “horns” (Fig. 28). Abdominal ventrite 5 with very distict longitudinal ridges (Fig. 32). Body length 2.1–2.2 mm ............................ ......................................................................................................................................................S. megalopus Hansen Head without distinct tufts of setae anteriorly of eyes. Abdominal ventrite 5 without distinct longitudinal ridges (Fig. 33). Body length 1.5–2.1 mm ...................................................................................................................................... 7 Interstices on head and pronotum lacking microsculpture, shiny. Pronotal punctures rounded. Median ridge on metaventrite reaching its posterior margin in both sexes. Female abdominal ventrite 5 entire posteriorly. Body length 1.9–2.1 mm .......................................................................................................................................... S. epulum sp. n. Interstices of head and pronotum with more or less distinct microsculpture, interstices therefore opaque. Pronotal punctures rasp-like. Median ridge almost reaching posterior margin of metaventrite in both sexes or sexually dimorphic, reaching ca. anterior third of metaventrite in males and posterior margin of the metaventrite in females (compare Figs. 50 and 51). Female abdominal ventrite 5 entire or emarginate posteromedially (Fig. 33, 34). Body length 1.5–1.9 mm. The “S. cruciphallus complex”................................................................................................................ 8 Apical sclerite of the median lobe long and very narrow; lateral sclerites present, very narrow, situated almost per-


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pendicularly to the apical sclerite (Figs. 9–10). Body length 1.5–1.7 mm .................................. S. cruciphallus sp. n. Apical sclerite of the median lobe wider; lateral sclerites absent or present, if developed than rather wide and short (Figs. 14, 18). Body length 1.5–1.9 mm ...................................................................................................................... 9 9 Lateral sclerites of median lobe of aedeagus absent, apical membranous portions of the median lobe only slightly wider than its width at midlength (Figs. 7–8). Median carina of the metaventrite long, nearly reaching its posterior margin in both sexes (Fig. 50). Posterior margin of abdominal ventrite 5 emarginate in females (as Fig. 34).............. .......................................................................................................................................................... S. auribleps sp. n. Lateral sclerites of median lobe of aedeagus developed, apical membranous portion of median lobe much wider than its width at midlength (Figs. 13–14, 17–18). Median carina of the metaventrite shortened posteriorly in males (Fig. 51) or fully developed in both sexes. Posterior margin of abdominal ventrite weakly emarginate or entire in females ................................................................................................................................................................................... 10 10 Abdominal ventrite 5 entire posteriorly in both sexes. Apical and lateral sclerites of median lobe very large, lateral sclerite semicircular (Figs. 13–14). Median carina of the metaventrite sexually dimorphic, distinct only in anterior third of the metaventrite in males (Fig. 51) ....................................................................................S. emissarium sp. n. Apical and lateral sclerites of median lobe moderately large, lateral sclerite irregular in shape, bearing small lateral tooth (Figs. 17–18). Median carina of the metaventrite long, nearly reaching its posterior margin in both sexes......... .............................................................................................................................................................. S. garciai sp. n. -

Taxonomy Genus Sacosternum Hansen, 1989 Sacosternum Hansen, 1989: 257. —Type species: S. megalopus Hansen, 1989 (by monotypy).— Gender: neuter.

Differential diagnosis. Eyes moderately large to very large, separated by 1.3–4.4× of width of one eye (Figs. 1–6, 27–28); antennal club blunt at apex (Fig. 38); pronotal punctures uniform in size; each pronotal puncture bearing a seta; median portion of prosternum separated from lateral portion, forming an elevated plate extending over mesal parts of lateral portions; prosternal plate carinate medially; anteromedian excision of prosternum absent (Figs. 39, 43–45); antennal grooves present, moderately large, not reaching lateral portion of hypomeron (Fig. 39); elytron with 9 punctural series; lateral margin of elytron without denticles; mesepisternal grooves for reception of procoxae moderately large, not reaching mesocoxal cavities posteriorly (Figs. 50–55); anterolateral ridge of metaventrite divergent from posterior margin of mesocoxal cavities laterally (Figs. 50–55); median portions of anterolateral ridges bent posteriad, forming median longitudinal carina of variable length on metaventrite (Figs. 50–55); abdominal ventrite 1 with longitudinal carina and additional longitudinal ridges (Figs. 31–33); posterior margin of abdominal ventrites 1–4 with small but distinct denticles (these rarely reduced on ventrite 4) (Figs. 31–35); median lobe of aedeagus with complex sclerotized and membranous apical structures (Figs. 8, 10, 12, 14, 16, 18, 20, 22, 24, 26); base of median lobe attached to base of parameres; male sternite 8 with anteromedian narrow projection (Fig. 37); median portion of male sternite 9 without median tongue-like projection (Fig. 36); body length 1.5–2.6 mm. Recognition. Although rather variable in external morphological characters, the representatives of Sacosternum may be easily distinguished from remaining Neotropical genera of Megasternini by the combination of the following characters: (1) anterolateral ridge of the metaventrite divergent from mesocoxal cavity, bent posteriad (or rarely anteriad) laterally (Figs. 50–55); (2) median portion of prosternum shield-like, with median carina and without anteromedian emargination (Figs. 39, 41–43); (3) mesepisternal grooves for reception of procoxae moderately large, not reaching mesocoxal cavities (Figs. 50–55); (4) median carina on the metaventrite present at least in anterior third, often completely dividing metaventrite into two halves (Figs. 51–55); (5) posterior margins of abdominal ventrites 1–3 with small denticles (Figs. 31–33).

REVISION OF THE GENUS SACOSTERNUM

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FIGURES 1–6. Body habitus. 1–2: Sacosternum sp. B; 3–4: S. garciai; 5–6: S. lebbinorum. 1, 3, 5: dorsal habitus; 2, 4, 6: lateral habitus.

Besides of these characters distinguishing all known Sacosternum species, the following characters are usually helpful during the routine identification: (a) dorsal side usually reddish brown (Figs. 1, 3) (dark brown only in S. lebbinorum and S. sp. A; Fig. 5); (b) eyes usually very large, separated by 1.3–2.8× of width of one eye (moderately large, separated by 4.4× width of one eye only in S. lebbinorum); (c) head usually with a triangular interocular area defined by shallow impressions (Fig. 27; absent in Sacosternum sp. A and S. sp. B, sometimes weakly developed also in other species); (d) lateral portion of pronotum usually with 1–2 longitudinal impressions on each side (Figs. 29–30; impressions absent Sacosternum sp. A and S. sp. B, sometimes weakly developed also in other species);

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(e) abdominal ventrites 1–4 (or 1–5 in S. megalopus) usually with very distinct longitudinal sharp ridges entirely covering ventrites (Figs. 31.35; not developed only in Sacosternum sp. A and S. sp. B, in which only the ventrite 1 bears rather weakly developed ridges). By the general body shape, presence of the arcuately bent anterolateral ridges of metaventrite and demarcated median portion of prosternum, Sacosternum species may be only confused with some species of the genus Oosternum and Australocyon within the Neotropical Region. Oosternum species do not bear the characters (5) and (b) to (e) mentioned above, Australocyon does not bear the characters (3) to (5) and (b) to (e). Description. Body elongate oval, elytra gradually narrowing posteriad; body outline not interrupted between pronotum and elytra. Elytra unicolored. Head: Anterior margin of clypeus with distinct rim, lateral portions of clypeus slightly deflexed. Interocular area not elevated above the remaining surface but bearing a triangular impressed area in many species (except Sacosternum sp. A and S. sp. B). Eyes moderately large to very large, separated 1.3–4.4× of width of one eye. Mentum narrowing anteriad. Gula rather wide, gular sutures divergent posteriad, posterior tentorial pits minute. Maxilla of male with sucking disc; maxillary palpomere 2 strongly widened apically, palpomere 4 spindle-like. Antenna with nine antennomeres, antennal club compact; antennomere 9 forming ca. anterior third of the club, indistinctly constricted subapically, blunt and not projecting at apex. Prothorax: Pronotum arcuatelly narrowed anteriad, slightly emarginate at anterior margin, evenly convex or with a more or less distinct set of longitudinal impressions; not deflexed laterally. Lateral margin of pronotum not serrate, bearing distinct rim. Pronotal puntures uniform in size, similar on whole surface of pronotum; each puncture bearing decumbent seta. Transverse row of punctures on posterior margin of pronotum absent or hardly defined (in S. lebbinorum). Prosternum highly carinate medially, median portion separated from lateral portions; median portion plate-like, slightly overlapping lateral portions; anterolateral excision of prosternal plate absent; ridges lying along anterior margin of pronotal plate absent. Pair of deep pits just lateral to the prosternal plate absent. Antennal grooves present, moderately large, not reaching lateral margin of hypomeron, rounded to subangular. Lateral glabrous portion of hypomeron narrow anteriorly, moderately widened posteriorly. Mesothorax: Scutellar shield small, in shape of equilateral triangle. Elytron with nine series of punctures, not deflexed or explanate laterally. Distance between elytral series 7 and 8 equal to distance between other series. Elytra not costate, with weakly to moderately convex intervals and modeately to highly impressed elytral series. Elytral interval 2 as wide as intervals 1 and 3 posteriorly, as convex and as high as adjacent intervals, reaching elytral apex. Interval punctation with punctures bearing pale decumbent setae. Lateral margin of elytra finely serrate. Epipleuron moderately wide, slightly narrowing posteriad, reaching posterior portion of metathorax; pseudepipleuron reaching elytral apex. Grooves for reception of procoxae moderately large, not reaching to anterior margin of mesocoxal cavities. Preepisternal elevation variable in shape, triangular, arrow-head shaped or narrowly to very narrowly suboval; posterolateral bulges of preepisternal elevation well developed. Metathorax: Metaventrite with subpentagonal elevated median portion; lateral portions of metaventrite dull, with fine microsculpture. Anterolateral ridges distinctly developed, divergent from posterior margin of mesocoxal cavities laterally, bent posteriad along lateral margin of metaventrite in most species (except Sacosternum sp. A and S. sp. B, in which they are bent anteriad); the ridges meeting and bent posteriad mesally, forming median carina of variable length: length of carina sexually dimorphic in some species, usually completely developed and nearly reaching posterior margin of metaventrite in females (except Sacosternum sp. B). Femoral lines absent or developed only laterally of anterolateral ridge and delimiting a triangular area in some species (S. lebbinorum, S. delta, S. inconnivum). Anepisternum very narrow, 8.5– 11.5× as long as wide. Hind wings present, all examined species macropterous (all dissected specimens were inspected for this character). Legs short; procoxae with an elevated transverse ventral ridge; hind tibiae straight; tarsi slightly shorter than tibiae, bearing sparse yellowish pubescence ventrally.



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Abdomen: Abdominal ventrite 1 carinate medially, bearing sublateral longitudinal ridges. Posterior margins of ventrites finely to very distinctly denticulate. Male genitalia: Each paramere bearing 2 setae apically. Median lobe of aedeagus basally attached to parameres, ca. 1.5× longer than parameres, projecting slightly further than parameres distally; apical portion of median lobe with a complex structure consisting of an apical sclerite and a pair of lateral sclerites (the latter missing in some species) and a set of membranous structures. Apical sclerite bearing anterolateral crenulate rim, the rim continuous apically, its margins straight; lateral margins of median lobe lacking backward directed setae; apex of median lobe lacking setae. Sternite 8 with anteromedian narrow projection, the tergite subdivided into two halves. Sternite 9 simple, crescent-like, lacking median tongue-like projection. Female genitalia: Not examined.

Species descriptions Sacosternum auribleps sp. n. (Figs. 7–8, 33–34, 41, 43, 50) Type locality. Brazil, Rondônia State, 62 km SW of Ariquemes near to Fzda. Rancho Grande [ca. 9°58'S 62°48'W; altitude ca. 150 m a.s.l.]. Type material. Holotype: male (FSCA): “BRAZIL: Rondônia 62 / km SW Ariquemes, nr / Fzda. Rancho Grande / 3-15-XII-1996 JE Eger / Black Light Trap”. Paratypes (7 spec.): BRAZIL: 2 females, 3 spec. (FSCA): same data as holotype; 1 male (KSEM): “BRAZIL: Rondonia, 62 / km. SW Ariquemes, nr. / Fdza. Rancho Grande / 8-20-XI-1994; J. Eger / C. O'Brien, black light”; 1 male (NMPC): “BRAZIL: Rondonia, 62km / SW Ariquemes, Fzda / Rancho Grande, 11-XI- / 1994, C.W.O'Brien / blacklight trap”. Differential diagnosis. Extremely similar to Sacosternum cruciphallus, S. emissarium and S. garciai by the combination of the absence of triangular areas at lateral margins of metaventrite, very narrow preepisternal plate of mesothorax, pronotum with fine microsculpture and with two very distinct sublateral longitudinal impressions. Males may be distinguished from S. garciai by posteriorly reduced median carina of the metaventrite (complete in S. garciai) and from all these species by the morphology of the apical portion of the median lobe which is rather weakly widened and lacks lateral sclerites. Females may be distinguished from S. emissarium by the posterior emargination of abdominal ventrite 5 (absent in S. emissarium); females of S. garciai and S. cruciphallus cannot be distinguished. Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.6–1.8 mm (holotype: 1.7 mm), body width 0.9–1.2 mm (holotype: 1.1 mm); TL/TW ratio = 1.65. Coloration. Dorsal side reddish brown, frons and lateral margins of pronotum brown; ventral side reddish brown; coxae, femora and tibiae reddish brown, palpi, antennae and tarsi yellowish. Head. Clypeus with dense punctation consisting of moderately large rasp-like punctures, each puncture bearing fine decumbent seta; interstices with fine microsculpture; anterior margin of clypeus slightly convex. Interocular area with median triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of moderately large rasp-like punctures, punctures of same shape on mesal and lateral portion; interstices with fine mesh-like microsculpture. Eyes large, separated by 1.6× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 1.5× wider than long, anterior margin slightly emarginate; anteromedian part slightly impressed, bearing sparse punctation consisting of large nearly circular punctures; interstices with fine mesh-like microsculpture. Maxillary palpomeres 2 and 4 ca. twice as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum continuously arcuate on posterior margin; shallowly sulcate; bearing two weak but distinct longitudinal impressions sublaterally. Pronotum forming continuous curve with elytra in lateral view; posterolateral corners rounded, lateral margin weakly sinuate, with narrow marginal rim. Pronotal punctation dense, slightly denser than that on frons, consisting of rather large deeply impressed rasp-like punctures; interstices with microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow; projecting slightly anteriad mesally, straight in lateral view. Median portion of

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prosternum 1.5× wider than long; additional lateral expansions of the prosternal shield not developed; postero-mesal projection with shallow notch. Lateral margin of antennal grooves subangulate. Mesothorax. Scutellar shield lacking punctures, interstices with fine mesh-like microsculpture. Elytral series 1–5 and 7 arising basally, series 6 and 8 arising subbasally; series 9 not joining series 8 anteriorly, nearly reaching elytral base. Serial punctures small; transverse, sparsely arranged, slightly larger than interval punctures. Lateral serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals moderately convex at suture, becoming slightly more convex laterad and posteriad; series weakly impressed mesally and laterally. Interval punctation consisting of small, transversely scar-like punctures arranged in series at least on some intervals. Epipleura ca. as wide as pseudepipleura. Preepisternal plate very narrow, suboval, or nearly linear, 3.3× longer than wide; median part bearing densely arranged large setiferous punctures; plate narrowly attached to metaventrite; posterior part of preepisternal elevation slightly overlapping anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture; punctation of median portion moderately dense, consisting of rather large nearly circular setiferous punctures; interstices without microsculpture, shiny. Lateral portions of anterolateral ridges arcuately bent posteriad, concave sublaterally. Length of median carina of metaventrite ridge sexually dimorphic, reaching anterior third of metaventrite length in male and posterior margin of metaventrite in female. Anterior margin of metaventrite indistinctly crenulate. Lateral portions of femoral lines not developed, the lateral triangular area on metaventrite absent. Anepisternum 8.4× longer than wide. Legs. Protibiae not emarginate on outer margin apically. Abdomen. Abdominal ventrite 1 not crenulate anteriorly. Ventrites 2–4 with additional ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 emarginate medially in females. Male genitalia. Aedeagus 0.67 mm long. Parameres 1.4× longer than phallobase, gradually narrowing from base to apex. Phallobase wide, 0.9× longer than wide. Median lobe nearly parallel-sided in basal 0.7, slightly widened in apical 0.3; pair of lateral subapical sclerites absent; apical sclerite wide. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular. Variation. Uniform in most external characters examined. The only observed variability concerns the preepisternal plate of mesothorax which is partly reduced posteriorly in two specimens examined (the plate therefore appears shorter and widely separated from the anterior margin of the metaventrite). Etymology. Derived from aura (Lat., glow) and blepsis (Greek; seeing, sight), i.e. seeing the glow, referring to the fact that all specimens were attracted at black light. Standing as a noun in apposition. Biology. Unknown. All species were collected at light. Distribution. Known only from the type locality.

Sacosternum cruciphallus sp. n. (Figs. 9–10, 27, 30) Type locality. Panama, Chiriquí Province, Fortuna [coordinates ca. 8°43'N 82°15'W; altitude ca. 1100 m a.s.l.]. Type material. Holotype: male (FMNH): “PAN: Chiriqui Prov. / Fortuna, 16-X-1976 m // FMHD #763002, H. / Wolda”. Paratypes (2 spec.): PANAMA: 2 spec. (FMNH, NMPC): same locality data as holotype. Differential diagnosis. Extremely similar to Sacosternum auribleps, S. emissarium and S. garciai by the combination of the absence of triangular areas at the sides of the metaventrite, very narrow preepisternal plate of mesothorax, pronotum with fine microsculpture and two very distinct sublateral longitudinal impressions. Males may be distinguished from S. garciai by the posteriorly reduced median carina of metaventrite (complete in S. garciai) and from all these species by the morphology of the apical portion of the median lobe which is widely expanded and bears very narrow lateral sclerites and very narrow apical sclerite. Females may be distinguished only from S. emissarium based on the posteriorly emarginate abdominal ventrite 5 (entire posteriorly in S. emissarium). REVISION OF THE GENUS SACOSTERNUM


9

FIGURES 7–14. Aedeagophores. 7–8: S. auribleps; 9–10: S. cruciphallus; 11–12: S. delta; 13–14: emissarium. 7, 9, 11, 13: whole aedeagus, dorsal view; 8, 10, 12, 14: detail of the apical portion of the median lobe.

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Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.5–1.7 mm (holotype: 1.5 mm), body width 0.9–1.1 mm (holotype: 0.9 mm); TL/TW ratio = 1.7. Coloration. Dorsal side reddish brown, frons dark brown; ventral side reddish brown; coxae, femora and tibiae reddish brown, palpi, antennae and tarsi yellowish. Head. Clypeus with dense punctation consisting of moderately large rasp-like punctures, each puncture bearing fine decumbent seta; interstices with fine microsculpture; anterior margin of clypeus slightly convex. Interocular area with median triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of moderately large rasp-like punctures; interstices with fine mesh-like microsculpture. Eyes large, separated by 1.7× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 1.4× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed, bearing sparse punctation consisting of large nearly circular punctures; interstices with fine mesh-like microsculpture. Maxillary palpomere 2 and 4 ca. twice as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum forming continuous curve with elytra in lateral view, continuously arcuate on posterior margin, shallowly sulcate sublaterally, bearing two (rarely three) weak but distinct longitudinal impressions. Posterolateral corners rounded; lateral margin weakly sinuate with narrow marginal rim. Pronotal punctation moderately dense, ca. as dense as that on frons; punctation consisting of rather large deeply impressed rasp-like punctures; interstices with microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow, projecting anteriad mesally, straight in lateral view; median portion of prosternum 1.3× wider than long; additional lateral expansions of prosternal shield not developed; posteromesal projection with shallow notch. Lateral margin of antennal grooves rounded. Mesothorax. Scutellar shield without punctures, interstices without microsculpture. Elytral series 1–5 and 7 arising basally, series 6 and 8 arising subbasally; series 9 joining series 8 anteriorly, nearly reaching elytral base. Serial punctures small, transverse, sparsely arranged, ca. as large as interval punctures, connected to each other by a fine and sharp longitudinal furrow. Elytral intervals moderately convex at suture, becoming slightly more convex laterad and posteriad; series weakly impressed mesally and laterally. Interval punctation arranged in series at least on some intervals, consisting of small, transversely scar-like punctures. Epipleura ca. as wide as pseudepipleura. Preepisternal plate very narrow, suboval, 3.3× longer than wide; median part slightly concave bearing densely arranged large setiferous punctures, interstices without microsculpture; median longitudinal carina absent; preepisternal elevation narrowly attached to metaventrite, its posterior part slightly overlapping anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture; punctation of median portion moderately dense, consisting of rather large nearly circular setiferous punctures; interstices without microsculpture, shiny. Anterolateral ridge arcuately bent posteriad along lateral margin, concave sublaterally. Length of median ridge of metaventrite sexually dimorphic, reaching anterior third of metaventrite length in male and posterior margin of metaventrite in female. Anterior margin of metaventrite indistinctly crenulate. Lateral portions of femoral lines absent, triangular area at lateral sides of metaventrite absent. Anepisternum 8.8× longer than wide. Legs. Protibiae not emarginate on outer margin apically. Abdomen. Abdominal ventrite 1 not crenulate anteriorly. Ventrites 2–4 with longitudinal ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 emarginate medially in females. Male genitalia. Aedeagus 0.63 mm long. Parameres 1.5× longer than phallobase, wide basally, gradually narrowing apicad. Phallobase wide, 0.9× longer than wide. Median lobe nearly parallel-sided in basal 0.6, strongly widened in apical 0.4. A pair of lateral subapical sclerites present; apical sclerite narrow; lateral sclerites very narrow and long, in almost perpendicular position to apical sclerite. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular. Variability. None observed.



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Etymology. Derived from crux (Lat., cross) and phallos (Greek, penis), reflecting the cross-shaped arrangement of the sclerites in the apical part of the median lobe of this species. Standing as a noun in apposition. Biology. Unknown. Distribution. Known only from the type locality.

Sacosternum delta sp. n. (Figs. 11–12, 29, 44, 54) Type locality. Paraguay, Itapúa Department, Yalai, San Rafael Reserve, 26°38'17"S 55°39'50"W, 100 m a.s.l. Type material. Holotype: male (KSEM): “PARAGUAY: Itapúa / Yalai, prop. Hostettier family / San Rafael Reserve, 100 m / 26°38'17"S, 55°39'50"W / 25–26 NOV 2000; Z.H. Falin / PAR1F00 048A / ex: flight intercept trap”. Paratype (1 spec.): BRAZIL: 1 female (FSCA): “BRAZIL: Rondonia, 62 / km. SW Ariquemes, nr. / Fzda. Rancho Grande / 8–20-XI-1994; J. Eger, / C. O'Brien; black light” Differential diagnosis. Differs from all known Sacosternum species except S. inconnivum by the shape of the anterolateral ridge on the metaventrite, which is angulate sublaterally. It may be distinguished from the latter species by median prosternal carina which is straight in lateral view (in contrast to slightly elevated in S. inconnivum). Males may be distinguished from the latter species by a very narrow aedeagus and the apical portion of median lobe without triangularly narrowed sclerotized median portion. Females may be distinguished from the latter species by the posteriorly emarginate abdominal ventrite 5 (in contrast to the entire ventrite 5 in females of S. inconnivum). Description. Body widest ca. at midlength, weakly convex in lateral view. Body length 1.7–2.0 mm (holotype: 1.7 mm), body width 1.1–1.3 mm (holotype: 1.1 mm); TL/TW ratio = 1.65. Coloration. Dorsal side reddish brown; ventral side reddish brown; legs, mouthparts and antennae reddish brown. Head. Clypeus with moderately dense punctation consisting of moderately large semicircular, slightly rasp-like punctures, each puncture bearing fine decumbent seta; interstices without microsculpture; anterior margin of clypeus truncate. Interocular area with median triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of moderately large semicircular, slightly rasp-like punctures; interstices without microsculpture. Eyes large, separated by 2.8× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 1.8× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed; surface with dense punctation consisting of rather large circular punctures; interstices without distinct microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum slightly more convex than elytra in lateral view, weakly bisinuate on posterior margin; surface evenly convex or shallowly sulcate laterally, bearing indistinct sublateral longitudinal impression posteriorly on each side; posterolateral corners forming obtuse angle, lateral margin arcuate or slightly angulate, with narrow marginal rim. Pronotal punctation moderately dense, slightly denser than on frons, consisting of moderately large, rounded, rather sharply impressed punctures; interstices without microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow, projecting anteriad mesally, straight in lateral view. Median portion of prosternum 0.7× wider than long; additional lateral expansions of prosternal shield well developed; posteromesal projection with shallow notch. Lateral margin of antennal grooves subangulate. Mesothorax. Scutellar shield bearing few moderately large circular punctures, interstices without microsculpture. Elytral series 1–5 and 7 arising basally, series 6 and 8 arising subbasally; series 9 joining series 8 anteriorly, nearly reaching elytral base. Serial punctures large, rounded, sparsely arranged, much larger than interval punctures. Serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals weakly convex at suture, becoming slightly more convex laterad and posteriad; series deeply impressed mesally and laterally. Punctation irregular on all intervals, consisting of small, scar-like

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punctures. Epipleura ca. as wide as pseudepipleura. Preepisternal plate narrow; 1.8× longer than wide, arrowhead shaped with median longitudinal carina, bearing rather dense and coarse setiferous punctation; the plate widely attached to metaventrite, its posterior part slightly overlapping over anterior margin of metaventrite, Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax, with median portion markedly differing from lateral portion in punctation and microsculpture. Punctation of median portion of metaventrite consisting of densely arranged, moderately large circular setiferous punctures; interstices without microsculpture, shiny. Lateral portions of anterolateral ridges bending posteriad towards lateral margin of metaventrite, with sharp angle sublaterally. Length of median ridge of metaventrite sexually dimorphic, reaching posterior fifth in male and posterior margin of metaventrite in female. Anterior margin of metaventrite crenulate. Lateral portion of femoral lines developed between anterolateral ridge and margin of metaventrite, delimiting a triangular area at lateral portions of metaventrite. Anepisternum 8.2× longer than wide. Legs. Protibiae with shallow apical emargination on outer margin. Abdomen. Ventrite 1 not crenulate anteriorly. Ventrites 2–4 with longitudinal ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 weakly emarginate medially in females. Male genitalia. Aedeagus 0.75 mm long. Parameres 1.1× longer than phallobase, narrow, gradually narrowing apicad. Phallobase narrow, 1.5× longer than wide. Median lobe narrow in basal 0.7, slightly widened in apical 0.3 and then narrowing apicad. A pair of lateral subapical sclerites absent; apical sclerite narrow. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular. Variation. Only a slight variation in the depth of the lateral impressions of the pronotum was observed between the two specimens examined. Etymology. Derived from delta, the Greek letter shaped as a triangle, referring to the large triangular area on the lateral portion of metaventrite typical for this species. Standing as a noun in apposition. Biology. Unknown. The holotype was caught in flight intercept trap. Distribution. Known from one locality in western Brazil and one locality in southern Paraguay.

Sacosternum emissarium sp. n. (Figs. 13–14, 51) Type locality. Costa Rica, Puntarenas Province, Coto Brus Canton, Estación Pittier, 1670 m a.s.l. [coordinates ca. 9°04'N 82°56'W]. Type material. Holotype: male (INBio): “COSTA RICA: Prov. Puntarenas, Coto / Brus, Estación Pittier, 1670m, 22 ENE / 2000. R. Gonzales. Red de Golpe / L_S_330030_578645 #56804”. Paratypes (3 spec.): COSTA RICA: 1 female (KSEM): “COSTA RICA: Prov. Puntarenas, Coto / Brus, Estación Pittier, 1670m, 20 ENE / 2000. R. Gonzales. Mantillo / L_S_330030_578645 #56805”; 1 spec. (NMPC): “COSTA RICA: Prov. Puntarenas, Coto / Brus, Estación Pittier, 1670m, 18 ENE / 2000. R. Gonzales. Mantillo / L_S_330030_578645 #56368”; 1 spec. (INBio): “COSTA RICA: Prov. Puntarenas, Coto / Brus, Estación Pittier, 1670m, 30 / NOV-12 DIC 1999. R. Gonzales de / Luz L_S_330030_578645 #57372”. Differential diagnosis. Extremely similar to Sacosternum auribleps, S. cruciphallus and S. garciai by the combination of the absence of triangular areas at the sides of metaventrite, very narrow preepisternal plate of mesothorax, pronotum with fine microsculpture and two very distinct sublateral longitudinal impressions. Males may be distinguished from S. garciai by the posteriorly reduced median carina of metaventrite (reaching posterior margin of metaventrite in S. garciai) and from all these species by the very wide aedeagus and the morphology of the apical portion of the median lobe which is widely expanded and bears wide apical as well as lateral sclerites. Females may be distinguished from all above species by the absence of an emargination of abdominal ventrite 5 (present in the remaining species of "S. cruciphallus complex"). Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.6–1.7 mm (holotype: 1.7 mm), body width 1.0–1.1 mm (holotype: 1.0 mm); TL/TW ratio = 1.6.



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Coloration. Dorsal side reddish brown, frons dark brown; ventral side reddish brown; coxae, femora and tibiae reddish, mouthparts, antennae and tarsi yellowish. Head. Clypeus with dense punctation consisting of moderately large rasp-like punctures without setae; interstices with fine microsculpture; anterior margin of clypeus slightly convex. Interocular area with median triangular area defined by shallow depressions. Frons with dense punctation consisting of moderately large rasp-like punctures; interstices with fine mesh-like microsculpture. Eyes large, separated by 2.4× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 2.3× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed; surface with sparse punctation consisting of large nearly circular punctures, interstices with fine mesh-like microsculpture. Maxillary palpomeres 2 and 4 ca. twice as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum continuously arcuate on posterior margin, forming continuous curve with elytra in lateral view, shallowly sulcate, bearing two weak but distinct longitudinal impressions on each side. Posterolateral corners rounded, lateral margin weakly sinuate, with narrow marginal rim. Pronotal punctation moderately dense, slightly denser than that on frons, consisting of moderately large rasp-like punctures; interstices with microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow; projecting anteriad mesally, straight in lateral view. Median portion of prosternum 1.3× wider than long; additional lateral expansions of the prosternal shield not developed; postero-mesal projection with shallow notch. Lateral margin of antennal grooves rounded. Mesothorax. Scutellar shield bearing few moderately large circular punctures, interstices with fine meshlike microsculpture. Elytral series 1–5 and 7 arising basally, series 6 and 8 arising subbasally; series 9 joining series 8 anteriorly, nearly reaching elytral base. Serial punctures small, transverse, sparsely arranged, ca. as large as interval punctures; serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals weakly convex at suture, becoming slightly more convex laterad and posteriad, series weakly impressed mesally and laterally. Interval punctation arranged to series at least on some intervals, consisting of small, transversely scar-like punctures. Epipleura ca. as wide as pseudepipleura. Preepisternal plate very narrow, 4.8× longer than wide, suboval, flat, bearing densely arranged large setiferous punctures; plate narrowly attached to metaventrite, posterior part slightly overlapping anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax; median portion markedly differing from lateral portion in punctation and microsculpture. Punctation of median portion consisting of small, circular setiferous punctures; interstices without microsculpture, shiny. Anterolateral ridge arcuately bending posteriad towards lateral margin of metaventrite, concave sublaterally. Length of median ridge of metaventrite sexually dimorphic, reaching anterior third of metaventrite length in male and posterior margin of metaventrite in female. Anterior margin of metaventrite indistinctly crenulate. Lateral portion of femoral lines absent, triangular area at lateral sides of metaventrite absent. Anepisternum 9.8× longer than wide. Legs. Protibiae not emarginate on outer margin apically. Abdomen. Ventrite 1 not crenulate anteriorly. Ventrites 2–4 with longitudinal ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 without emargination in both sexes. Male genitalia. Aedeagus 0.73 mm long. Parameres 1.2× longer than phallobase, wide basally, slightly narrowing apicad. Phallobase as long as wide. Median lobe narrow basally, markedly widened in apical fifth. A pair of lateral subapical sclerites present; apical sclerite wide; lateral sclerites wide, semicircular, in almost perpendicular position to apical sclerite. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular. Variation. None observed. Etymology. Derived from emissarius (Lat., spy, scout) reflecting the large eyes typical for Sacosternum and the shape of the sclerites in the apical portion of the median lobe resembling the lily-flower symbol of scouting movement. Treated as an adjective. Biology. Unknown. Specimens examined were collected at light, using flight intercept trap and (probably sifted) from humus. Distribution. Known only from the type locality.

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Sacosternum epulum sp. n. (Figs. 15–16) Type locality. Brazil, Santa Catharina State, Nova Teutonia, 300–500 m a.s.l. [coordinates ca. 27° 03'S 52°24'W]. Type material. Holotype: male (FMNH): “BRASIL: Sta. Catharina / Nova Teutonia / X:1972, 300–500m / leg. F. Plaumann”. Paratypes (9 spec.): BRAZIL: 1 male (FMNH): same data as the holotype; 1 male, 4 spec. (FMNH, NMPC): “Nova Teutonia, Sta. / Catharina, BRAZ. / III:15:1952 / Fritz Plaumann leg. // bei Eciton / praedator”; 2 spec. (FMNH, NMPC): same label data with date “III:22:52”; 1 spec. (FMNH): same label data with date “III:19:1952”; 1 female (FMNH): same label data with date “IV:7:1953”. Differential diagnosis. The species can be easily recognized from all other Sacosternum species by the combination of absence of the triangular area at lateral sides of the metaventrite, pronotal interstices without microsculpture (in contrast to species of “S. cruciphallus complex”), head without tufts of erect hairs (“horns”) anteriorly of each eye and abdominal ventrite 5 without longitudinal ridges (both latter characters distinguish it from S. megalopus). In all these characters S. epulum agrees with S. sp. B, but it may be easily recognized from this species by narrowly suboval preepisternal elevation and abdominal ventrites 2–4 with longitudinal ridges. Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.9–2.1 mm (holotype: 2.0 mm), body width 1.2–1.3 mm (holotype: 1.3 mm); TL/TW ratio = 1.6. Coloration. Dorsal side reddish brown, frons dark brown; ventral side dark reddish brown; legs reddish brown, mouthparts and antennae yellowish. Head. Clypeus with dense punctation consisting of rather small, slightly rasp-like punctures, each puncture bearing fine decumbent seta; interstices without microsculpture; anterior margin of clypeus truncate. Interocular area with median triangular area defined by shallow depressions. Frons with dense punctation consisting of moderately large semicircular rasp-like punctures, interstices without microsculpture. Eyes large, separated by 2.9× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 2.0× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed in contrast to lateral portions; surface with dense punctation consisting of rather large, rounded punctures; interstices with fine mesh-like microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum forming continuous curve with elytra in lateral view, continuously arcuate on posterior margin; surface shallowly sulcate, bearing two weak but distinct longitudinal impressions on each side. Posterolateral corners rounded, lateral margin weakly sinuate, with narrow marginal rim. Pronotal punctation moderately dense, as dense as on frons, punctures moderately large, rounded; interstices without microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow, projecting anteriad mesally, straight in lateral view. Median portion of prosternum 1.45× wider than long; additional lateral expansions of the prosternal shield not developed; postero-mesal projection with shallow notch. Lateral margin of antennal grooves rounded. Mesothorax. Scutellar shield bearing a few minute punctures, interstices with fine mesh-like microsculpture. Elytral series 1–7 arising basally, series 8 arising subbasally; series 9 joining series 8 anteriorly, nearly reaching elytral base. Serial punctures moderately large, transverse, sparsely arranged, slightly larger than interval punctures. Serial punctures not connected to each other with a fine and sharp longitudinal furrow. Elytral intervals weakly convex at suture, becoming slightly more convex laterad and posteriad; series weakly impressed mesally and laterally. Interval punctation arranged in series at least on some intervals, consisting of small transverse, scar-like punctures. Epipleura slightly wider than pseudepipleura. Preepisternal plate very narrow; 4.8× longer than wide, suboval; median part flat, bearing densely arranged moderately large setiferous punctures; plate narrowly attached to metaventrite, its posterior part slightly overlapping over anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture. Punctation of median portion of metaventrite



15

consisting of densely arranged, moderately large punctures each bearing long pale seta; interstices without microsculpture, shiny. Anterolateral ridge arcuately bending posteriad towards lateral margin of metaventrite, concave sublaterally. Length of median ridge of metaventrite similar in both sexes, reaching posterior margin of metaventrite. Anterior margin of metaventrite indistinctly crenulate. Lateral portion of femoral lines absent, triangular area at sides of metaventrite missing. Anepisternum 10.0× longer than wide. Legs. Protibiae with shallow apical emargination on outer margin. Abdomen. Ventrite 1 not crenulate anteriorly. Ventrites 2–4 with longitudinal ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 entire in both sexes. Male genitalia. Aedeagus 0.70 mm long. Parameres 1.3× longer than phallobase, rather narrow basally, continually narrowing apicad. Phallobase narrow, 1.2× longer than wide. Median lobe narrow in basal 0.7, slightly widened in apical 0.3. A pair of lateral subapical sclerites present; apical sclerite wide, lateral sclerites narrow but not extremely long, forming a sharp angle to apical sclerite. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular. Variation. Not observed. Etymology. Epulum (Lat., feast, banquet), reflecting one of the paratypes collected as a “guest on a banquet” of the army ants of the genus Labidius. Standing as a noun in apposition. Biology. One of the paratypes was collected in association with the army ant Labidius praedator (F. Smith, 1858) (Formicidae, Ecitoninae). Distribution. Known only from the type locality.

Sacosternum garciai sp. n. (Figs. 3–4, 17–18, 36–37, 38–39, 46) Type locality. Panama, Chiriquí Province, Boquete [coordinates ca. 8°46'N 82°26'W, altitude ca. 1100m]. Type material. Holotype: male (UCDC): “Boquete PAN / Chirique Prov. / III 19 1977 / Henk Wolda”. Paratypes (12 spec.): PANAMA: 1 female (CNC): same data as the holotype; 1 male (NMPC): same label data with date “VIII 12 1977”; 2 females (CNC): same label data with date “X 17 1977”; 1 female (NMPC): same label data with date “X 18 1977”; 1 spec. (CNC): same label data with date “IX 11 1977”; 1 female (CNC): same label data with date “VI 26 1977”; 1 male (CMN): “PANAMA: Chiriqui Prov. / 27.7 km W Volcan / Hartmann’s Finca / 08°45'N, 82°48'W / 1450m, 14–17 VI 1995 / J. Ashe & R. Brooks#231 / ex: flight intercept trap”. COSTA RICA: 1 male (KSEM): “COSTA RICA: Limon / Reventazon, Hamburg / Farm XI:10:1927 / leg. F. Nevermann // Field Mus. Nat. Hist. / 1966 / A. Beirig Colln. / Acc. Z-13812 // at light”; 1 female (FMNH): same label data with date “XI:10:27”; 1 female (FMNH): same label data with date “V:27:1935”. VENEZUELA: 1 male (MALUZ): “Venezuela Zulia / Dtto Maracaibo / San Jose de los / Altos 35 Km. N / O. de Laberinto / 1400m 18/19-VIII-1990 // Colector: / J. Camacho”. Differential diagnosis. Extremely similar to Sacosternum auribleps, S. cruciphallus and S. emissarium by the combination of the absence of triangular areas at the lateral sides of metaventrite, very narrow preepisternal plate of mesothorax, pronotum with fine microsculpture and at least two very distinct sublateral longitudinal impressions. Males may be distinguished from these species by median carina of metaventrite reaching posterior margin of metaventrite (at least slightly reduced posteriorly in the remaining species) and rather narrow aedeagus and only moderately widened apical portion of the median lobe, bearing wide but rather small lateral sclerites. Females may be distinguished from S. emissarium by the posterior emargination of abdominal ventrite 5 (absent in S. emissarium). Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.4–1.9 mm (holotype: 1.7 mm), body width 0.9–1.1 mm (holotype: 1.1 mm); TL/TW ratio = 1.6. Coloration. Dorsal side dark reddish brown, frons slightly darker; ventral side dark reddish brown; coxae, femora, tibiae and antennal clubs reddish brown, mouthparts, antennomeres 1–6 and tarsi yellowish.

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FIGURES 15–22. Aedeagophores. 15–16: S. epulum; 17–18: S. garciai; 19–20: S. inconnivum; 21–22: S. megalopus. 15, 17, 19, 21: whole aedeagus, dorsal view; 16, 18, 20, 22: detail of the apical portion of the median lobe.



17

FIGURES 23–26. Aedeagophores. 23–25: S. lebbinorum, holotype; 26: S. cf. lebbinorum from Brazil, Rondonia, SW of Ariquemes. 23: whole aedeagus, dorsal view; 24, 26: detail of the apical portion of the median lobe; 25: detail of apical sclerite after clearing of the aedeagus in KOH.

Head. Clypeus with moderately dense punctation consisting of moderately large semicircular rasp-like to scar-like punctures, each puncture bearing fine decumbent seta; interstices with fine microsculpture; anterior margin of clypeus slightly convex. Interocular area with triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of moderately large semicircular scar-like punctures; interstices with fine mesh-like microsculpture. Eyes large, separated by 2.2× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 2.0× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed; surface with sparse punctation consisting of large, nearly circular punctures; interstices with fine mesh-like microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpemere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum forming continuous curve with elytra in lateral view, continuously arcuate on posterior margin; shallowly sulcate, bearing two weak but distinct longitudinal impressions on each side. Posterolateral corners rounded, lateral margin weakly sinuate with narrow marginal rim. Pronotal punctation dense, slightly denser than that on frons, punctation consisting of small, semicircular rasp-like punctures; interstices with microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow, projecting anteriad mesally, straight in lateral view. Median portion of prosternum 1.2× wider than long; additional lateral expansions of prosternal shield absent; posteromesal projection with shallow notch. Lateral margin of antennal grooves rounded. Mesothorax. Scutellar shield bearing few minute punctures, interstices with fine mesh-like microsculpture. Elytral series 1–5 and 7 arising basally, series 6 and 8 arising subbasally; series 9 joining

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series 8 anteriorly, slightly abbreviated anteriorly, arising in basal 0.1 of elytral length. Serial punctures small, transverse, sparsely arranged, slightly larger than interval punctures. Serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals moderately convex at suture, becoming slightly more convex laterad and posteriad; series weakly impressed mesally and laterally. Interval punctation arranged to series at least on some intervals, consisting of minute transversely scar-like punctures. Epipleura ca. as wide as pseudepipleura. Preepisternal plate very narrow, 4.0× longer than wide, suboval, median part flat, bearing densely arranged small setiferous punctures; plate narrowly attached to metaventrite, posterior part slightly overlapping anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax, its median portion markedly differing from lateral portion in punctation and microsculpture. Punctation of median portion of metaventrite consisting of rather sparsely arranged small setiferous punctures; interstices without microsculpture, shiny. Anterolateral ridge bending arcuately posteriad towards lateral margin of metaventrite, concave sublaterally. Length of median ridge of metaventrite similar in both sexes, reaching posterior margin of metaventrite. Anterior margin of metaventrite indistinctly crenulate. Lateral portion of femoral line absent, triangular area at lateral sides of metaventrite absent. Anepisternum 10.0× longer than wide. Legs. Protibiae not emarginate on outer margin apically. Abdomen. Ventrite 1 not crenulate anteriorly. Ventrites 2–4 with longitudinal ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 weakly emarginate medially in females. Male genitalia. Aedeagus 0.67 mm long. Parameres 1.3× longer than phallobase, rather narrow basally, continually narrowing apicad. Phallobase narrow, 1.2× longer than wide. Median lobe narrow in basal 0.6, moderately widening in apical 0.4. A pair of lateral subapical sclerites present; apical sclerite wide; lateral sclerites wide, each with small lateral tooth in almost perpendicular position to apical sclerite. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular. Variation. A rather wide variation in the shape of the lateral sclerites of the median lobe was observed among the examined specimens, which seems to be at least partly caused by the different direction and “folding” of these sclerites in different aedeagophores examined. As the specimens examined agree in all remaining characters including of the entirely developed median carina of the metaventrite in males (which is unique for this species within the “S. cruciphallus complex”), we consider these variation as intraspecific. Etymology. The species is dedicated to Mauricio García (MALUZ), a specialist on Neotropical Hydrophilidae and primary collaborator of the project on Aquatic Insects of Venezuela. Biology. Unknown. Some of the specimens examined were collected at light or in flight intercept traps. Distribution. Known from Costa Rica (Limon Province), Panama (Chiriquí Province) and western Venezuela (Zulia State). Probably rather widely distributed in southern Central America and north-western South America.

Sacosternum inconnivum sp. n. (Figs. 19–20, 47, 55) Type locality. Panama, Canal Zone, Barro Colorado Island [coordinates ca.9°09'N 79°50'W, altitude ca. 0–70 m a.s.l.]. Type material. Holotype: male (KSEM): “PANAMA: Panama / Barro Colorado Isd. / 09°11'N, 79°51'W / 6 Aug. 1994, D. Banks / ex: flight intercept trap”. Paratypes (4 spec.): PANAMA: 1 female (KSEM): “PANAMA: Colon / Parque Nac. Soberania / Pipeline Rd. Km 6.1 / 09°07'N 79°45'W, 40m / 7–21 June 1995 / J. Ashe, R. Brooks #265 / ex: flight intercept trap”; male (UCDC): “Barro Colorado I / CZ Panama VIII / 25,27 1986 / Henk Wolda // TRAP / 2B”. COSTA RICA: 1 male (NMPC): “COSTA RICA: Heredia Province / 16km SSE La Virgen, 1070m / 10°16'N 84°05'W / 10–21.iv.2001; 11/TN/19/029 / INBio-OETALAS transect”; 1 male (INBio): “Rancho Quemado, 200m / Peninsula de Osa, Prov. / Puntarenas, Costa Rica / Oct 1992, F. Quesada / L-S 292500, 511000”.



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Differential diagnosis. Easily distinguishable from all known Sacosternum species except S. delta by the shape of the anterolateral ridge on the metaventrite which is convex and subangulate sublaterally. For differential characters from S. delta, see this species or the respective couplets in the key.

FIGURES 27–37. 27, 30: S. cruciphallus; 28, 32: S. megalopus; 29: S. delta; 31: Sacosternum sp. A; 33–34: S. auribleps (33: male; 34: female); 35: Sacosternum sp., female belonging to the “cruciphallus complex”, Mexico, Veracruz, Canyon SW Rio Metlac; 36–37: S. garciai. 27: head, dorsal view; 28: head, frontal view; 29–30: pronotum; 31–33: abdomen, ventral view; 34–35: abdominal ventrites 4–5; 36: malesternite 9; 37: male sternite 8.

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FIGURES 38–49. 38–39, 46: S. garciai; 40, 45, 49: Sacosternum sp. B; 41, 43: S. auribleps; 42, 48: S. lebbinorum; 44: S. delta; 47: S. inconnivum. 38: head, ventral view; 39: prosternum, ventral view; 40–42: mentum; 43–45: prosternal shield and procoxae; 46–49: preepisternal elevation of mesothorax.



21

FIGURES 50–55. Meso- and metaventrite. 50: S. auribleps; 51: S. emissarium; 52: S. lebbinorum; 53: Sacosternum sp. B; 54: S. delta; 55: S. inconnivum.

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Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.7–2.0 mm (holotype: 2.0 mm), body width 1.1–1.2 mm (holotype: 1.2 mm); TL/TW ratio = 1.6. Coloration. Dorsal side reddish brown; ventral side reddish brown; legs, mouthparts and antennae yellowish. Head. Clypeus with moderately dense punctation consisting of moderately large nearly circular punctures, each puncture bearing fine decumbent seta; interstices without microsculpture; anterior margin of clypeus slightly concave. Interocular area with triangular area defined by shallow depressions. Frons with dense punctation consisting of moderately large circular punctures; interstices without microsculpture. Eyes large, separated by 2.4× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 2.0× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed; surface with moderately dense punctation consisting of moderately large circular punctures; interstices without distinct microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpomere 3. Scapus shorter than antennomeres 2–6 combined. Prothorax. Pronotum distinctly more convex than elytra in lateral view, weakly bisinuate on posterior margin; surface evenly convex, or shallowly sulcate, bearing indistinct longitudinal impression posteriorly on each side. Posterolateral corners forming obtuse angle; lateral margin angulate, with narrow marginal rim. Pronotal punctation dense, as dense as on frons, consisting of rather small rounded punctures; interstices without microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow; projecting anteriad mesally, with anterior portion extending into small tooth in lateral view. Median portion of prosternum 1.9× wider than long; additional lateral extensions of prosternal shield developed; postero-mesal projection with shallow notch. Lateral margin of antennal grooves subangulate. Mesothorax. Scutellar shield bearing few minute circular punctures, interstices without microsculpture. Elytral series 1–5 arising basally, series 6–8 arising subbasally; series 9 not joining series 8 anteriorly, abbreviated anteriorly, arising in basal 0.15 of elytral length. Serial punctures moderately large, rounded, sparsely arranged, much larger than interval punctures. Serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals weakly convex at suture, becoming slightly more convex laterad and posteriad; series deeply impressed mesally and laterally. Interval punctation arranged in series at least on some intervals, consisting of small, scar-like punctures. Epipleura ca. as wide as pseudepipleura. Preepisternal plate narrow, 1.8× longer than wide, arrow-head shaped, with median longitudinal carina, bearing rather dense and coarse setiferous punctation; elevation widely attached to metaventrite, posterior part slightly overlapping anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax; its median portion markedly differing from lateral portion in punctation and microsculpture. Punctation of median portion of metaventrite consisting of densely arranged small circular setiferous punctures; interstices without microsculpture, shiny. Anterolateral ridge arcuately bending posteriad towards lateral margin of metaventrite, subangulate sublaterally. Length of median ridge of metaventrite sexually dimorphic, reaching posterior fifth in male and posterior margin of metaventrite in female. Anterior margin of metaventrite crenulate. Lateral portion of femoral line present between anterolateral ridge and lateral sides of metaventrite, delimiting a triangular area. Anepisternum 11.5× longer than wide. Legs. Protibiae with shallow apical emargination on outer margin. Abdomen. Ventrite 1 not crenulate anteriorly. Ventrites 2–4 with longitudinal ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 without emargination in both sexes. Male genitalia. Aedeagus 0.85 mm long. Parameres as long as phallobase, narrow basally, continually narrowing apicad. Phallobase narrow, 1.5× longer than wide. Median lobe narrow basally, slightly widening up to apical fourth, sclerotized median portion then triangularly narrowing apicad. A pair of lateral subapical sclerites present; apical sclerite narrow; lateral sclerites narrow but not extremely long, forming a sharp angle to apical sclerite. Gonopore indistinct. Median portion of sternite 9 shallowly circular. Variability. None observed. Etymology. Derived from inconnivus (Lat., never closing the eyes), reflecting the large eyes of this species typical for the genus Sacosternum. Adjective.



23

Biology. Unknown. Some specimens examined were collected at flight intercept trap. Distribution. Known from Costa Rica (provinces of Heredia and Puntarenas) and Panama (Canal Zone).

Sacosternum lebbinorum sp. n. (Figs. 5–6, 23–26, 42, 48, 52) Type locality. Peru, Loreto Region, 160 km NE of Iquitos, Explornapo Camp at Rio Sucusari, 2 km from Rio Napo [coordinates ca. 3°21'S 72°39'W; altitude ca. 100 m a.s.l.]. Type material. Holotype: male (FSCA): “PERU: Loreto Pr., 160km / NE Iquitos, Explornapo / Camp, Rio Sucusari, 2 km / from Rio Napo; 27–31- / VIII-1992; P. E. Skelley // Ecitor burchelli / bivoac nearby / litter or soil”. Paratypes (23 spec.): PERU: 15 spec. (FSCA, KSEM, NHMW, NMPC): same data as holotype. BRAZIL: 1 male, 4 females, 2 spec. (FMNH, KSEM, NMPC): “Brazil: Pará, Carajas / March 1984 // from detritus beneath / an ant nest / Coll. by N. Degallier”. FRENCH GUIANA: 1 male, 2 spec. (KSEM, NMPC): “FRENCH GUIANA / Roura, 27.4 km SSE, 280 m / 4°44'20"N, 52°13'25"W / 26–29 MAY 1997; J. Ashe, R. Brooks / FG1AB97 079 ex: flight intercept trap”. Additional material examined. 1 male (FSCA): “Rondonia, 62 / km. SW Ariquemes, nr / Fzda Rancho Grande / 8–20-XI-1994 J. Eger / C. O'Brien; black light”. Differential diagnosis. Easily recognizable from remaining Sacosternum species by the combination of the large triangular areas at lateral sides of the metaventrite, continually arcuate anterolateral ridge of the metaventrite and drop-like to suboval preepisternal plate of mesothorax. Moreover, S. lebbinorum has only moderately large eyes in comparison with remaining Sacosternum species. For additional differential characters see the key. Description. Body widest ca at midlength, weakly convex in lateral view. Body length 2.1–2.6 mm (holotype: 2.5 mm), body width 1.1–1.6 mm (holotype: 1.4 mm); TL/TW ratio = 1.8. Coloration. Dorsal side dark reddish brown; ventral side dark reddish brown; coxae, femora and tibiae dark reddish brown, mouthparts, antennae and tarsi reddish brown. Head. Clypeus with moderately dense punctation consisting of moderately large circular punctures, each puncture bearing fine decumbent seta; interstices without microsculpture; anterior margin of clypeus slightly concave. Interocular area with triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of moderately large circular punctures; interstices without microsculpture. Eyes moderately large, separated by 4.4× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 2.3× wider than long, pentagonal in shape; anteromedian part slightly impressed; surface with sparse punctation consisting of large circular punctures situated only posteriorly; interstices without distinct microsculpture. Maxillary palpomeres 2 and 4 ca. twice as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum slightly more convex than elytra in lateral view, weakly triangular on posterior margin; surface shallowly sulcate, bearing indistinct longitudinal impression posteriorly on each side. Posterolateral corners forming obtuse angle; lateral margin angulate, with wide and distinct lateral rim. Pronotal punctation moderately dense, as dense as that on frons, punctation consisting of moderately large circular punctures; interstices without microsculpture. Transverse row of punctures on posterior margin of pronotum hardly defined. Median carina of prosternum wide but not forming a plate, projecting anteriad mesally, straight in lateral view. Median portion of prosternum 1.6× wider than long; lateral extensions of prosternal shield present; postero-mesal projection with shallow notch. Lateral margin of antennal grooves subangulate. Mesothorax. Scutellar shield bearing few moderately large punctures, interstices without microsculpture. Elytral series 1–7 arising basally, series 8 arising subbasally; series 9 joining series 8 anteriorly, nearly reaching elytral base. Serial punctures moderately large, transverse, sparsely arranged, much larger than interval punctures. Serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals moderately convex at suture, becoming slightly more convex laterad and posteriad; series deeply

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impressed mesally and laterally. Interval punctation arranged in series at least on some intervals, consisting of rather small, transverse scar-like punctures. Epipleura slightly wider than pseudepipleura. Preepisternal plate narrow, 2.1–2.5× longer than wide, drop-like, without median longitudinal carina; median part flat or slightly concave, bearing densely arranged small setiferous punctures, interstices without microsculpture; plate narrowly attached to metaventrite, posterior part slightly overlapping anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax; its median portion indistinctly differing from lateral portion by slightly enlarged punctures. Punctation of median portion of metaventrite consisting of moderately large circular setiferous punctures becoming markedly larger posteriad; interstices without microsculpture, shiny. Anterolateral ridge arcuately bending posteriad towards lateral margin of metaventrite, concave sublaterally. Length of median ridge of metaventrite similar in both sexes, reaching posterior margin of metaventrite. Anterior margin of metaventrite indistinctly crenulate. Lateral portion of femoral line present between anterolateral ridges and lateral sides of metaventrite, delimiting a triangular area. Anepisternum 9.0× longer than wide. Legs. Protibiae with shallow apical emargination on outer margin. Abdomen. Ventrite 1 not crenulate anteriorly. Ventrite 2 and 3 with longitudinal ridges, ventrites 4–5 flat; posterior margin of ventrites 1–3 finely denticulate, ventrite 4 finely denticulate or lacking denticles; abdominal ventrite 5 without emargination in both sexes. Male genitalia. Aedeagus 0.86 mm long. Parameres 1.5× longer than phallobase, rather narrow basally, continually narrowing apicad. Phallobase wide, as long as wide. Median lobe narrow basally, slightly constricted in apical 0.3, slightly widening and continually narrowing apicad. A pair of lateral subapical sclerites absent; apical sclerite wide. Gonopore indistinct. Median portion of sternite 9 shallowly angular. Variation. Slight variability was observed in the shape and proportions of the preepisternal elevation of mesothorax, which may vary between drop-like to suboval and may be 2.1–2.5× longer than wide. Posterior margin of abdominal ventrite 4 usually lacks denticles; sometimes it bears few isolated denticles and rarely a complete denticulation identical to that on the abdominal ventrite 3 is developed. Aedeagus is rather constant in the structures of the apical portion of the median lobe in all type specimens (Figs. 23–25). The specimen from Ariquemes (Brazil) mentioned under the additional material examined externally agrees with remaining specimens of S. lebbinorum, but the apical sclerite of its aedeagus is more distinct than in type specimens (in which the basal borders of the sclerite are only vaguely seen even after clearing in KOH) and seems to be narrower apically and more bilobate basally (Fig. 26). We consider these differences as intraspecific variation for the time being. Etymology. The species is dedicated to fellow Neotropical biologist Dr. Daniel Lebbin and Ms. Erin Allen on the occasion of their marriage. Biology. Most specimens examined were collected in litter and soil nearby a bivouac of an army ant Eciton burchelli Westwood, 1842 (Formicidae, Ecitoninae) or from a detritus beneath an unspecified “ant nest”. Single specimens were collected at light or using flight intercept traps. Distribution. Confirmed for few widely distributed localities in Peru (Loreto Province), Brazil (Pará Province) and French Guiana. The record from the Brazilian province of Rondonia needs confirmation. Probably widely distributed in northern part of South America.

Sacosternum megalopus Hansen, 1989 (Figs. 21–22, 28, 32) Type locality. Panama, Chiriquí Province, Fortuna [coordinates ca. 8°43'N 82°15'W; altitude ca. 1100 m a.s.l.]. Type material examined: Holotype: male (UCDC): “Fortuna PAN / Chirique Prov. / IX-12-1977 / Henk Wolda // HOLOTYPE / Sacosternum / megalopus / M. Hansen”. Paratype: 1 spec. (UCDC): same locality as holotype but with date “IV-20-1979” and type label “PARATYPE / Sacosternum / megalopus / Hansen”. Note. The second paratype from Boquete (Panama) was not examined for this study and we cannot therefore reconfirm its assignment to S. megalopus. REVISION OF THE GENUS SACOSTERNUM


25

Additional material examined: COSTA RICA: 1 female (INBio): “COSTA RICA: Prov. Puntarenas, Coto / Brus, Estación Pittier, 1680 m. 01–13 Oct / 2000 R. Gonzales Manual L_S / _578645_330030 #59656”; 1 spec. (KSEM, pure alcohol collection of A. Short): “COSTA RICA: Cartago Province / Tapantí National Park / 09°45.671'N/83°47.087'W / 1276 m, H-G vapor light, 7.i.2004 / AEZ Short leg. AS-04-009”. Differential diagnosis. The species may be very easily recognized from all remaining Sacosternum species by the presence of a small tuft of erect setae in from of each eye (seemingly forming small horns) and by abdominal ventrite 5 bearing very distinct longitudinal ridges. Both these characters are absent from all other known species. See the identification key for further diagnostic characters. Redescription. Body widest ca at midlength, weakly convex in lateral view. Body length 2.1–2.2 mm (holotype: 2.1 mm), body width 1.2–1.3 mm (holotype: 1.3 mm); TL/TW ratio = 1.7. Coloration. Dorsal side reddish brown, frons at eyes dark brown; ventral side reddish brown; legs, mouthparts and antennae reddish brown. Head. Clypeus with moderately dense punctation consisting of rather small semicircular rasp-like punctures, each puncture bearing fine decumbent seta; interstices without microsculpture; anterior margin of clypeus slightly convex. Interocular area with triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of rather small semicircular rasp-like punctures; interstices without microsculpture. Eyes large, separated by 1.3× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye present. Mentum 1.8× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed; surface with sparse punctation consisting of large circular punctures; interstices without distinct microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined. Prothorax. Pronotum forming continuous curve with elytra in lateral view, weakly bisinuate on posterior margin; surface shallowly sulcate, bearing two weak but distinct longitudinal impressions sublaterally on each side. Posterolateral corners rounded; lateral margin arcuate, with wide and distinct lateral rim. Pronotal punctation dense, as dense as that on frons, consisting of larger small, semicircular rasp-like punctures; interstices without microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow, projecting anteriad mesally, straight in lateral view. Median portion of prosternum 1.2× wider than long; lateral extensions of prosternal shield absent; postero-mesal projection with shallow notch. Lateral margin of antennal grooves rounded. Mesothorax. Scutellar shield bearing few minute punctures, interstices with fine mesh-like microsculpture. Elytral series 1–5 and 7 arising basally, series 6 slightly subbasally, series 8 distinctly subbasally; series 9 joining series 8 anteriorly, nearly reaching elytral base. Serial punctures small, transverse, sparsely arranged, ca. as large as interval punctures. Serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals weakly convex at suture, becoming more convex laterad and posteriad; series deeply impressed mesally and laterally. Interval punctation arranged to series at least on some intervals, consisting of small, transversely scar-like punctures. Epiplerua ca. as wide as pseudepipleura. Preepisternal plate very narrow, 4.0× longer than wide, suboval, median part flat, bearing densely arranged moderately large setiferous punctures, interstices without microsculpture; plate narrowly attached to metaventrite, posterior part slightly overlapping anterior margin of metaventrite. Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax; its median portion markedly differing from lateral portion in punctation and microsculpture. Punctation of median portion of metaventrite absent (with exception of few minute punctures laterally); interstices without microsculpture, shiny. Anterolateral ridge arcuately bending posteriad towards lateral margin of metaventrite, concave sublaterally. Length of median ridge of metaventrite similar in both sexes, reaching posterior margin of metaventrite. Anterior margin of metaventrite indistinctly crenulate. Lateral portion of femoral lines and triangular area at lateral sides of metaventrite absent. Anepisternum 9.1× longer than wide. Legs. Protibiae not emarginate on outer margin apically.

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FIGURE 56. Distribution of the Sacosternum species.



27

Abdomen. Ventrite 1 not crenulate anteriorly. Ventrites 2–5 with longitudinal ridges; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 without emargination in both sexes. Male genitalia. Aedeagus 0.74 mm long. Parameres 1.4× longer than phallobase, rather wide basally, continually narrowing apicad. Phallobase as long as wide. Median lobe narrow throughout the length except of the apparent widening in apical 0.3. A pair of indistinct lateral subapical sclerites present. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular. Variation. None observed. Biology. Unknown. Non-type specimens examined were collected at light and by manual collecting. Distribution. Known from three relatively closely situated localities in the mountains that straddle Costa Rica (Puntarenas and Cartago Provinces) and Panama (Chiriquí Province).

Sacosternum sp. A (Fig. 31) Material examined. PERU: 1 female (FMHN): “PERU: Cuzco Dept. / Pillahuata, Manu rd. / km 128, 16-XI1982 / FMHD #82-240, ex // litter along stream / L. E. Watrous & G. Mazurek”. Diagnosis. Body highly convex in lateral view; head evenly convex, without depressions between eyes; eyes large, separated by 2.8× of width of one eye; a tuft of yellowish erect setae anteriorly of each eye absent; pronotum evenly convex, without sublateral impressions, forming continuous curve with elytra in lateral view; lateral margin of pronotum weakly sinuate; pronotal interstices with microsculpture; median portion of prosternum 1.5× wider than long; lateral expansions of prosternal shield present; punctures of elytral series small, transverse, ca. as large as interval punctures; preepisternal plate 1.4× longer than wide, triangular, without median longitudinal carina, widely attached to metaventrite, its median part concave; metaventrite distinctly longer than preepisternal elevation of mesothorax; anterolateral ridge subparallel to posterior margin of mesocoxal cavity laterally; median carina of metaventrite reaching its posterior margin in female; femoral lines and triangular areas at lateral sides of metaventrite absent; protibiae not emarginate on outer margin apically; ventrite 1 with weak longitudinal ridges; ventrites 2–5 without longitudinal ridges; abdominal ventrite 5 without emargination in female. Body length 1.77 mm. Easily recognizable from remaining Sacosternum species except of Sacosternum sp. B by the shape of the anterolateral ridge of metaventrite, highly convex body in lateral view, triangular preepisternal elevation of mesothorax and absence of longitudinal ridges on abdominal ventrites 2–5. The species can be distinguished from Sacosternum sp. B by the characters provided in the key. Biology. Unknown. The only know specimen was sifted from leaf litter. Distribution. Known only from the above locality in Peru.

Sacosternum sp. B (Figs. 1–2, 40, 45, 49, 53) Material examined. COSTA RICA: 1 female (KSEM): “COSTA RICA: Cartago Province / Tapanti Nat. Prk; 1200m elv. / HG-vapor light @visitor cabinas / 11.i.2005; AS-05-148 / A. Short, J. Hannam, A. Swanson”. Differential diagnosis. Body highly convex in lateral view; head evenly convex, without depressions between eyes; eyes large, separated by 2.1× of width of one eye; a tuft of yellowish erect setae anteriorly of each eye absent; pronotum evenly convex, without sublateral impressions, forming continuous curve with elytra in lateral view; lateral margin of pronotum weakly sinuate; pronotal interstices without microsculpture; median portion of prosternum 1.9× wider than long; lateral expansions of prosternal shield developed; punctures of elytral series small, transverse, slightly larger than interval punctures; preepisternal plate 1.2× longer than wide, triangular, without median longitudinal carina, widely attached to metaventrite, its median

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part flat; metaventrite distinctly longer than preepisternal elevation of mesothorax; anterolateral ridge subparallel to posterior margin of mesocoxal cavity laterally; median carina of metaventrite reaching posterior fifth of length in female; femoral lines and triangular area at sides of metaventrite absent; protibiae not emarginate on outer margin apically; ventrite 1 with weak longitudinal ridges; ventrites 2–5 without longitudinal ridges; abdominal ventrite 5 entire in female. Body length 1.6 mm. Easily recognizable from remaining Sacosternum species except from Sacosternum sp. A by the shape of the anterolateral ridge, highly convex body in lateral view, triangular preepisternal elevation of mesothorax and absence of longitudinal ridges on abdominal ventrites 2–5. The species can be distinguished from Sacosternum sp. A by the characters provided in the key. Biology. Unknown. The only known specimen was collected at light. Distribution. Known only from the above locality in Costa Rica.

Unidentified material Sacosternum sp. Except of the material mentioned above, we have examined the following female specimens belonging to the “S. cruciphallus complex”. Most of the specimens below are females and are very similar to each other and we therefore did no attempt to identify them up to the species level until the males will be available from these localities. The only male from Mexico almost certainly belongs to an undescribed species standing possibly close to S. emissarium and S. cruciphallus based on the morphology of its aedeagus (but it lacks the lateral sclerites of the median lobe in contast to these species). The genitalia of this specimen was unfortunatelly lost during the preparation of the temporary slide and the species cannot be therefore described. Two females (one from Mexico, collected at the same locality as the mentioned male specimen, the second collected at the Guatemalan locality listed below) share extremely enlarged teeth on the posterior margin of abdominal ventrite 4 (Fig. 35). The precise shape of these teeth vary slightly even between the two specimens. Both specimens were collected together with those having simply denticulate posterior margin of the ventrite. For this reason, we are not able to decide whether the enlarged teeth represent a character of taxonomic importance, an infrequently occurring abberation or sexually dimorphic character. Material examined. MEXICO: 1 male, 1 female (possibly not conspecific) (FMNH): “MEXICO: Veracruz / Canyon SW Rio Metlac / 3200 feet, VII.31.1973 / A. Newton // berl., vacated Eciton / burchelli bivouac / 24 hrs. vacant”. GUATEMALA: 3 females (possibly not conspecific) (FSCA): “GUATEMALA: Dept. of / Guatemala, Puerta Parada / 5-VIII-1999 / J. C. Schuster”. COSTA RICA: 1 female (KSEM): “COSTA RICA: Puntarenas / Monte Verde, 1400m / 23 May 1989, J. Ashe / R. Brooks, R. Leschen / ex: black light // Costa Rica Exped. #400 / Snow Entomol. Mus.”; 1 female (KSEM): “COSTA RICA: Heredia Province / 16km SSE La Virgen, 1070m / 10°16'N 84°05'W / 11–20.ii.2001; 11/TN/16/006 / INBio-OETALAS transect”. PANAMA: 1 female (CUIC): “PANAMA: Chiri. / Fortuna, 28.ix. / 1976, H. Wolda”; 1 female (UCDC): “Fortuna PAN / Chirique Prov. / VIII-10-1977 / Henk Wolda”; 1 female (UCDC): “Fortuna PAN / Chirique Prov. / V-8-1979 / Henk Wolda”; 1 female (UCDC): “Fortuna PAN / Chirique Prov. / V-21979 / Henk Wolda”. VENEZUELA: 1 female (CMN): “VENEZUELA: Merida / Tabay, La Mucuy Valley / 1900M, 15.VI.–30.VII. / 1989, S. & J. Peck / agric. Zone, UV, 89-214”.

Reconstruction of phylogenetic relationships Phylogenetic analysis is based on 51 morphological characters of the adults; immature stages are not known. Specimens suitable for molecular studies are available only for Sacosternum megalopus. Continuous characters (1, 4, 27) were transformed to discrete for their easier interpretation; their exclusion does not affect the results. All recognized species of Sacosternum were included in the analysis, including the formally undescribed S. sp. A and S. sp. B. Outgroup taxa were chosen to include the representatives of the genera REVISION OF THE GENUS SACOSTERNUM


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Motonerus and Oosternum which seem to be closely related to Sacosternum based on the preliminary analysis performed by Fikáček (2010), the genus Cetiocyon was chosen to root the tree as it seems not to be related to the above genera but still belongs to the group of “Gondwanan” genera based on its genital characters. Two species of Oosternum were included to cover the character diversity of the genus. Data were analysed with the TNT software (Goloboff et al. 2008) without any a priori considerations, using an exhaustive search (“implicit enumeration” option of TNT). Characters were mapped on the strict consensus tree using the WinClada programm (Nixon 2002). Bootstrap and jacknife analyses and Bremer support were used to evaluate the support of the clades by the characters; 1000 resampling replicates were used for bootstrap and jacknife analyses, Bremer support was calculated by setting the suboptimal tree length successively lower (1 through 7) and repeating an exhaustive search for each setting. The data matrix in Nexus format is available at the web site of the first author (http://www.cercyon.eu/Publications.htm). Characters used for the analysis. 1 Body shape in lateral view: (1) weakly convex (Figs. 4, 6); (2) highly convex (Fig. 2). 2 Interocular area: (1) evenly convex, without depressions; (2) with triangular area defined by oblique depressions (Fig. 27). In most species of Sacosternum, there are two oblique depressions in the interocular area (Fig. 27) and the head surface is therefore “bumpy” when observed in anterior view (Fig. 28). The depressions are not developed in Sacosternum sp. A and S. sp. B as well as in the outgroup taxa.

3 Interstices on frons: (1) with fine mesh-like microsculpture; (2) without microsculpture. 4 Eyes: (1) small (interocular distance ≥ 8× of width of one eye); (2) moderately large (interocular distance ≥ 8× of width of one eye ranging between 3× and 8× of width of one eye); (3) very large (interocular distance ≤ 3× of the width of one eye). In most species of Sacosternum, the eyes are extremely large, separated by 1.3–2.8× of the width of one eye. The only exception is S. lebbinorum, in which the eyes are “normal-sized”, separated by 4.3× of the width of one eye. Similar size of eyes is found in most outgroup taxa with an exception of Oosternum simplex, in which the eyes are extremely reduced.

5 A tuft of yellowish erect setae anteriorly of each eye: (1) absent; (2) present (Fig. 28). 6 Interstices of mentum: (1) without microsculpture (Fig. 42); (2) with fine mesh-like microsculpture (Figs. 40–41). 7 Posterolateral corners of mentum: (1) angulate, projecting laterad; (2) blunt, weakly developed. In most megasternine taxa, including all Sacosternum, the mentum bears lateral angular projections in the posterior half (Figs. 40–42, see the place where the mentum is widest). In some outgroup taxa (Cetiocyon, Motonerus), the angular projections are reduced and the mentum is only indistinctly widened in posterior half.

8 Anterolateral corners of mentum: (1) absent; (2) present. Anterolateral subangulate “corners” are developed on the mentum of most Megasternine taxa, making the mentum of the irregularly octagonal shape (Figs. 40–41). In S. lebbinorum, the anterolateral corners are not developed, the mentum is continually narrowing anteriad from its posterolateral projections and its shape is irregularly pentagonal.

9 Antennomere 9: (1) blunt at apex (Fig. 38); (2) pointed at apex. The apex of the antennal club is blunt in all Sacosternum species as well as in both Oosternum included to the analysis. In Motonerus and Cetiocyon, the apex is prolonged and more or less pointed. 10 Pronotum: (1) evenly convex; (2) with sublateral longitudinal impressions (Figs. 29–30). 11 Number of sublateral impressions on pronotum: (1) one (Fig. 29); (2) two (Fig. 30). Sublateral impressions are more or less developed in all Sacosternum except of Sacosternum sp. A and S. sp. B. In all outgroup taxa, the impressions are missing. In some Sacosternum, there are two impressions forming an open triangle – the more lateral impression is always more distinct than the submedian one. In S. delta, S. lebbinorum and S. inconnivum, the lateral impression is missing and the submedian is rather short but still very distinct in most specimens examined.

12 Pronotum in lateral view: (1) forming continuous curve with elytra (Figs. 2, 4); (2) more convex than elytra (Fig. 6).

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13 Posterolateral corners of pronotum: (1) forming and obtuse angle (Fig. 6); (2) rounded (Figs. 2, 4). 14 Lateral margin of pronotum: (1) arcuate; (2) angulate (Fig. 6); (3) weakly sinuate (Figs. 2, 4). The lateral margin of the pronotum is angulate or weakly sinuate in the Sacosternum species (see the figures). In most outgroup taxa, its shape is arcuate, i.e. the margin is arcuately bent from anterior corner to posterior one, without any trace of sinuation or of an obtuse angle (see Fikáček et al. (2009) and Fikáček & Hebauer (2009) for details).

15 Pronotal punctation: (1) all punctures bearing long setae; (2) punctures with minute setae (only apparent using SEM, i.e. the punctures seemingly without setae when examined using binocular) intermixed among those bearing long setae. See Fikáček (2009) for the explanation of this character.

16 Pronotal interstices: (1) without microsculpture; (2) with microsculpture. 17 Median portion of prosternum: (1) distinctly distinguished from lateral portions and elevated above them; (2) not divided from lateral portions. Median portion of prosternum is either continuous with its lateral portions and bearing the same microsculpture (Cetiocyon, Oosternum simplex), or is distinctly elevated above the level of the lateral portions. In the latter case, the median portion usually bears a microsculpture different from that of the lateral portions, and is defined by sharp oblique ridges laterally (Oosternum aequinoctiale, Motonerus). In Sacosternum, it is moreover widened, expanding in the lobes partially overlapping the lateral portions (see the next character). The elevated area in the median portion of the prosternum is considered homologous in all taxa examined irrespective to its particular morphology, and is therefore coded as single character.

18 Median prosternal portion: (1) extended over lateral portions (Figs. 39, 43–45); (2) not extended over lateral portions. In most megasternine taxa with elevated median portion of the prosternum, this part is delimited by sharp lateral ridges but the lateral portions of prosternum are clearly visible. In Sacosternum, the median portion of the prosternum is shield-like, overlapping over the mesal parts of the lateral portions of prosternum. A deep groove is therefore formed beneath the lateral expansions of the median prosternal plate in Sacosternum.

19 Sublateral additional projections of prosternal plate divided by an oblique ridge: (1) absent (Fig. 43); (2) present (Figs. 39, 44–45). There are two morphological variants of the prosternal shield in Sacosternum. The shield is wide, with the lateral smooth portion divided from median sculptured part by an oblique ridge on each side in Sacosternum sp. A, S. sp. B, S. lebbinorum, S. delta and S. inconnivum. In the remaining species, the lateral expansions are absent and only the median sculptured part is developed. The differences in the superficial sculpture of median and lateral portions as well as the relative position of the procoxal ridge suggests that the lateral ridge of the narrow shield is homologous with the sublateral ridge of the wide one, with the lateral expansion being only the laterally expanded marginal rim of the shield.

20 Antennal grooves on hypomeron: (1) absent; (2) present (Fig. 39). All species of Sacosternum bear large and very distinct antennal grooves not reaching the lateral hypomeral margin. In outgroup taxa, the grooves are present in Oosternum and absent from Cetiocyon and Motonerus.

21 Interstices of scutellar shield: (1) without microsculpture; (2) with fine mesh-like microsculpture. 22 Elytral series 9: (1) joining series 8 anteriorly (Figs. 4, 6); (2) separated from series 8 throughout (Fig. 2). 23 Shape of serial punctures of elytron: (1) transversely scar-like; (2) circular. 24 Posterolateral bulges of the preepisternal elevation of mesothorax: (1) situated very close to the anteromedian margin of metaventrite (Figs. 46, 49, 50–51, 53); (2) situated more anteriad, far from anteromedian margin of metaventrite (Figs. 47–48, 52, 54–55). Posterolateral bulges of the preepisternal elevation of mesothorax are well developed in all taxa examined except of Cetiocyon and Motonerus. In some species of Sacosternum, the bulges are situated rather close to the anteromedian projection of the metaventrite, with a very small gap left between the metaventrite margin and the bulges. In other Sacosternum species as well as in the Oosternum examined, there is a large gap between anterior margin of the metaventrite and the bulges. I considered the bulges as the synapomorphy of the New Caledonian endemic genus Kanala in my previous studies (Fikáček 2010), but they turn to be rather widespread at least in the “Gondwanan” megasternine genera.

25 Median portion of preepisternal elevation of mesothorax: (1) with narrow median longitudinal elevation (Figs. 46–47, 50–51, 54–55); (2) with wide oval plate (Figs. 48, 52); (3) with a triangular plate (Figs. 49, 53).



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In most Sacosternum species, the preepisternal elevation is narrowly longitudinally elevated mesally (the elevation usually bears slightly larger setiferous punctures, but does not form a distinctly delimited plate). This elevation is considerably widening at midlength in S. lebbinorum to form a slightly concave plate. In Sacosternum sp. A and S. sp. B, the elevation is much more widening posteriorly forming a triangular plate.

26 Median elevated portion of preepisternal elevation of mesothorax: (1) narrowly attached to anterior margin of metaventrite (Figs. 46–48); (2) widely attached to anterior margin of metaventrite (Fig. 49). In most Sacosternum and all outgroup taxa, the median elevated portion of preepisternal elevation is narrowly attached to the metaventrite (and in most cases slightly overlaps its anterior margin). In Sacosternum sp. A and S. sp. B, the elevated plate widely contacts the metaventite.

27 Metaventrite: (1) distinctly shorter than preepisternal elevation of mesothorax; (2) ca. as long as preepisternal elevation of mesothorax (Figs. 50–52, 54–55); (3) distinctly longer than preepisternal elevation of mesothorax (Fig. 53). 28 Anterolateral ridge of metaventrite: (1) laying parallel to posterior margin of mesocoxal cavity (i.e., reaching anterolateral corner of metaventrite); (2) divergent from posterior margin of mesocoxal cavity (i.e. not reaching anterolateral corner of metaventrite). The anterolateral ridge of metaventrite runs along the posterior margin of the metacoxal cavity throughout the width of metaventrite and therefore nearly reaches its anterolateral corner in most megasternine taxa including Cetiocyon and Motonerus. In Sacosternum and Oosternum, it diverts from the posterior margin of metacoxal cavity at about the halfway between the midline and lateral margin of the metaventrite.

29 Lateral portion of anterolateral ridge of metaventrite: (1) subparallel to posterior margin of mesocoxal cavity (Fig. 53); (2) bending posteriad (Figs. 50–52, 54–55). In most taxa in which the anterolateral ridge diverts from the metacoxal cavity (including Oosternum and most Sacosternum included into the analysis), it more or less arcuately bends posteriad and attaches the lateral margin of the metaventrite ca. in anterior third of its length. In Sacosternum sp. A and S. sp. B, the ridge is instead bending anteriad, lying subparallel to the postcoxal cavity.

30 Shape of lateral portion of anterolateral ridge of metaventrite: (1) concave (i.e. the ridge arcuatelly bending posteriad; Figs. 50–52); (2) convex (Fig. 55) to angulate (i.e. the ridge “zig-zag” shaped; Fig. 54). 31 Median portions of anterolateral ridges of metaventrite: (1) bending posteriad, forming median longitudinal carina (Figs. 50–55); (2) not bending posteriad, median carina absent. Both lateral ridges are bending posteriad medially and form variably long median carina in Sacosternum and Motonerus. In all remaining taxa, they are meeting anteromedially, but do not bend posteriad and the median carina is therefore absent in these taxa.

32 Median longitudinal ridge of metaventrite in male: (1) reaching ca. anterior third of metaventrite (i.e., developed only anteriorly; Fig. 51); (2) reaching at least to posterior third of metaventrite (i.e. complete or reduced only in very posterior part; Figs. 51–52). 33 Median longitudinal ridge of metaventrite in female: (1) reaching posterior margin of metaventrite or nearly so (i.e. the ridge complete; Figs. 54–55); (2) reaching ca. to the midlength of the metaventrite (Fig. 53); (3) reaching ca. anterior third of metaventrite (i.e. developed only anteriorly). 34 Anterior margin of metaventrite just posteriorly of anterolatera l ridge: (1) strongly crenulate (Figs. 54– 55); (2) weakly crenulate (Figs. 50, 52); (3) not crenulate (Figs 51, 53). 35 Femoral lines: (1) totally absent (Figs. 50–51, 53); (2) developed laterally between anterolateral ridge and lateral margin of the metaventrite, delimiting a triangular area (Figs. 52, 54–55). In S. lebbinorum, S. delta and S. inconnivum, there is a narrow triangular area at the lateral portion of the metaventrite. This area is delimited anteriorly by an additional oblique ridge which seems to be homologous to the lateral portions of the femoral lines based on its position (the intersection of fully developed femoral lines with fully developed anterolateral ridge is known e.g. in Peltocercyon, delimiting a similar triangular area as in mentioned Sacosternum species).

36 Procoxae: (1) with distinct ventral ridge (Figs. 39, 43–45); (2) simply conical, without ventral ridge. Simply conical proxocae are present in all genera of the Megasternini I have examined so far, with Sacosternum being the only exception. In Sacosternum, there is a distinct longitudinal ridge on the procoxa situated ca. as far from the midline as the lateral margin of the prosternal plate (or as its sublateral ridge in species with widened prosternal shield). In all species, the ridge moreover forms a border between two differently sculptured surfaces (Figs. 43–46). The ridge is rather low and therefore difficult to see in the

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species with narrow prosternal plate, but the examination using SEM photographs showed that the ridge is distinctly developed even in these species (Fig. 43).

37 Apical portion of protibiae: (1) not emarginate on lateral margin; (2) with shallow apical emargination on lateral margin. 38 Additional sublateral longitudinal ridges on abdominal ventrite 1: (1) absent; (2) present. 39 Longitudinal ridges on abdominal ventrite 2: (1) absent; (2) present. 40 Longitudinal ridges on abdominal ventrite 3: (1) absent; (2) present. 41 Longitudinal ridges on abdominal ventrite 4: (1) absent; (2) present. 42 Longitudinal ridges on abdominal ventrite 5: (1) absent; (2) present. Longitudinal ridges may be developed on each of the abdominal ventrites in megasternine taxa. In all cases, their presence on the ventrite is conditioned by their presence on the preceding ventrite (i.e., when the ridges are developed on ventrite 3, they are always developed also on ventrites 1 and 2). Based on the examination of the Sacosternum species for this study as well as the species of Motonerus (Fikáček & Short 2006), the ventrites are otherwise independent in terms of the presence of the ridges, and each ventrite is therefore coded as the separate character.

43 Posterior margin of abdominal ventrites (1) without denticles; (2) with small denticles. Posterior margin of abdominal ventrites bear small denticles in all species of Sacosternum. These denticles are absent from all remaining taxa examined. No variation was observed concerning the presence of the denticles on different ventrites, and the character is therefore coded as a single character covering all ventrites. In some species of Sacosternum, the denticles are rather fine and the examination of the ventrites using the light microscope is needed to evaluate this character properly.

44 Abdominal ventrite 5: (1) entire in both sexes; (2) slightly emarginate in females. Sexual dimorphism in the shape of the abdominal ventrite 5 is present in some species of Sacosternum: in females, it is shallowly emarginate posteromedially. This dimorphism is not known for any other megasternine genus so far.

45 Median lobe of aedeagus: (1) simple; (2) with complex sclerotized and membranous structures apically. The structure of the apical portion of the median lobe is very complex in all Sacosternum species (but unknown in S. sp A. and S. sp. B). This stands in contrast to its relatively simple morphology in all megasternine genera examined so far. Because of the limited number of specimens, the structure of the apical portion of the median lobe was not examined in deep detail and no attempt was done in order to understand the morphology and homologize the particular structures with the taxa outside of Sacosternum. Only a simple homology statement was done among the Sacosternum species examined (see comments below).

46 Sublateral sclerites of median lobe: (1) absent; (2) present. There is a part of stronger sclerotized and therefore rather dark-coloured sclerites situated subapically in some species of Sacosternum. We consider the sclerites as homologous among all Sacosternum species.

47 Apical sclerite of median lobe: (1) narrow; (2) wide. The apical sclerotized part of the median lobe is called “apical sclerite” here. Based on the position of the gonopore on this sclerite and the presence of narrow lateral rim in some species, it may be homologous to the apex of the median lobe in other taxa (see e.g. Motonerus, Fikáč ek & Short (2006)). However, as the homology is unclear, we did not code this character for the taxa outside of Sacosternum.

48 Shape of lateral sclerites of median lobe: (1) narrow; (2) wide. 49 Membranous lateral projections of median lobe: (1) absent; (2) present. In Sacosternum, there is a complex set of membranous structures in the apical portion of the median lobe, which expand laterad from the median lobe and cover the lateral sclerites (if these are present). Similar lateral membranous projections were observed in Oosternum aequinoctiale group (see Fikáček et al. (2009) for details). We tentatively consider the membranous sctructures in Sacosternum and Oosternum aequinoctiale group as homologous.

50 Crenulate rim on apical portion of median lobe: (1) present; (2) absent. A crenulate rim at the apex of the median lobe is present in all Sacosternum species in which males were examined. This structure is very similar to the apical crenulate rim present in Motonerus species (see Fikáček & Short 2006) and both structures are therefore tentatively cosidered homologous.

51 Gonopore (1) very distinct; (2) indistinct. A sclerotized and therefore very distinct gonopore is present in most Sacosternum species except of S. lebbinorum and S. inconnivum, in which it is not visible in the microscopic slides and is probably only membranous.



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Results of the analysis The analysis resulted in 22 most parsimonous trees of the length of 95 steps (CI=0.60, RI=0.74). The strict consensus tree of these trees is shown in Fig. 57 (length of the consensus tree is 99 steps, CI=0.57, RI=0.71), with the character distribution mapped on this tree.

FIGURE 57. Strict consensus tree of the 22 most parsimonous trees resulted from the phylogenetic analysis of the Sacosternum species.

The analysis supports the genus Sacosternum as monophyletic based on derived states of 9 characters, 6 of which are unique for this clade (4-3: eyes very large, interocular distance ≤3× of the width of one eye [reversal in S. lebbinorum]; 13-2: posterolateral corners of pronotum rounded [reversal in S. lebbinorum + S. delta + S. inconnivum clade]; 18-1: median portion of prosternum extended over lateral portions; 24-1: posterolateral bulges of preepisternal elevation of mesothorax situated very close to anteromedian margin of metaventrite [reversal in S. lebbinorum + S. delta + S. inconnivum clade]; 36-1: procoxae with distinct ventral ridge; 43-2: posterior margin of abdominal ventrites with small denticles). The complex structure of the apical portion of the median lobe, with a set of sclerotized and membranous parts, may be mentioned as an additional synapomorphy of the clade although it was not coded into the matrix because the its unclear homology statement to outgroup taxa. In all trees obtained, two clades were recognized at the basal node of Sacosternum. The lineage of Sacosternum sp. A + S. sp. B is supported by 4 synapomorphies, 3 of which are unique for this clade (26-2: preepisternal plate of mesothorax widely attached to metaventrite; 27-3: metaventrite distinctly longer than preepisternal elevation of mesothorax; 29-1: lateral portion of anterolateral ridge of metaventrite subparallel to posterior matgin of mesocoxal cavity). The second lineage, containing all remaining Sacosternum species, is supported by 7 synapomorphies, 6 of which are unique for the clade (2-2: interocular area with triangular area defined by oblique depressions; 10-2: pronotum with sublateral longitudinal impressions; 22-1: elytral series 9 joining series 8 anteriorly [reversal in S. inconnivum]; 34-2, 3: anterior margin of metaventrite just posterior to anterolateral ridge weakly to strongly crenulate [reversal in S. emissarium]; 40-2: longitudinal ridges on abdominal ventrite 3 present; 41-2: longitudinal ridges on abdominal ventrite 4 present).

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The latter clade consists of an unresolved basal “S. cruciphallus complex” containing S. auribleps, S. cruciphallus, S. emissarium and S. garciai and of a clade of the remaining species defined by 3 synapomorphies (two reversals: 3-2: interstice of frons without microsculpture; 16-1: pronotal interstices without microsculpture; one is unique for the clade plus for S. garciai: 32-2: median carina of metaventrite reaching at least its posterior third). Within this group, the clade of S. lebbinorum + S. delta + S. inconnivum is defined by 8 synapomorphies, of which three are unique for the clade (11-1: pronotum with one sublateral impression; 14-2: lateral margin of pronotum angulate; 35-2: lateral margin of metaventrite with additional line defining the triangular area) and a few reversals of the characters defining Sacosternum (see above). The tree statistics show a moderate support of the clades mentioned above. Four clades are resolved in more than 50 % of the bootstrap trees based on resampled data: the genus Sacosternum (90% of trees), Sacosternum sp. A + S. sp. B clade (98% of trees), Sacosternum lebbinorum + S. delta + S. inconnivum clade (62% of trees), and S. delta + S. inconnivum clade (73% of trees). Bremer support reaches the value of 6 for Sacosternum, 3–4 for remaining better-supported clades, but the value of 5 also for the clade comprising all Sacosternum without Sacosternum sp. A + S. sp. B, which was resolved only in 32% of bootstrap trees.

Discussion Sacosternum is endemic to the Neotropics. The species diversity seems to be rather low based on the above data, with 9 described and 3 undescribed species recognized (see Sacosternum sp. A, S. sp. B, and unidentified material for details). The genus is distributed from southern Mexico (Veracruz state) to Paraguay and southern Brazil (Santa Catharina state). Most species currently available are known from single or few specimens collected at light or using flight intercept traps. These collecting events seem to be rather accidental and the biology of the species remains unknown. Habitat data are only available for three species, all of which were found in association of the epigaeic ecitonine army ants: S. lebbinorum and the unidentified species from Mexico (see unidentified material above) with Eciton burchelli, and Sacosternum epulum with Labidius praedator. Two of these species (S. epulum and S. lebbinorum) were repeatedly collected in longer series under these circumstancies. Both species associated with Eciton burchelli were collected by sifting of the litter below the bivouac (24 hours after the relocation of the bivouac in the Mexican species), label data of S. epulum are not as detailed and indicate only the association with the ant species (“bei Eciton praedator”, = with Labidius praedator). The precise nature of the association of these species with army ants remains unknown. No external structures such as gland openings or morphological structures facilitating the grasping by the ants were found which would suggest them to be inquilines. The label data available rather indicate that the species of Sacosternum may be obligate inhabitants of the organic-rich leaf litter below the bivouacs of the army ants. Similarly, absence data also supports this association: many other related taxa (e.g. Oosternum and Motonerus) that commonly inhabit leaf litter have been collected in abundance (in the many thousands of specimens) using tranditional sifting and winkler extraction methods throughout Central America in the past decade (see e.g. Fikáček & Short 2006, Fikáček et al. 2009, Fikáček & Hebauer 2009, Fikáček 2009), while only a handful of Sacosternum specimens have been collected this way. This suggests that members of the genus have different biologies from other related Megaternini. The species of Sacosternum bear a set of morphological characters very unusual in other megasternine taxa: (1) median portion of prosternum is extremely shield-like widening laterad, forming a deep groove between the shield and lateral portions of the prosternum (Figs. 39, 43–45); (2) procoxa bears a large transverse ridge corresponding with the margin of prosternal shield in its position (Figs. 39, 43–45); (3) the shape of the lateral portion of anterolateral ridges of metaventrite is convex to angulate in S. delta and S. inconnivum (Figs. 54–55); (4) a triangular area is developed at the lateral side of metaventrite in S. lebbinorum, S. delta and S. inconnivum (Figs. 52, 54–55); (5) abdominal ventrites often with longitudinal grooves and posterior denticles (Figs. 31–35); (6) eyes are extremely large in all species except of S. lebbinorum (Figs. 1–6, 27–28). Taking into account the possible association with army ants, some of these structures might be considered as defensive morphological adaptation facilitating the firm attachement of the



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legs to the body: characters (1) and (2) together seem to form a set of grooves and ridges allowing to hide the anterior tibiae and/or tarsi, characters (3) and (4) seem to form similar ridge-limited area for deposit the medium tibia and/or tarsi. Similar grooves for depositing of tibiae/tarsi are frequently (but not exclusively) developed in several families of ant-associated beetles (e.g., chlamydopsine histerids, Tishechkin (2009); some Latridiidae, Kistner (1982); many aphidophagous or coccidophagous Coccinellidae, e.g. Kovář (1995)). Ridge-limited grooves on the metaventrite similar to those seen in mentioned Sacosternum species are also developed in many species of Cryptopleurum in which the tibiae are really deposited in these grooves in some dead specimens; however, these Cryptopleurum species seem not to be myrmecophilous (M. Fikáček, unpubl. data). On the other hand, the presence of the prosternal shield and the procoxal ridge is unique for Sacosternum. Interpretation of the remaining above characters is even more difficult: longitudinal ridges on abdominal ventrites (character 5 above) may serve to improve the strength of the ventrites; extremely enlarged eyes may indicate Sacosternum species as good and/or frequent flyers, judging from the fact that reduced eyes were only observed in micropterous species of the Megasternini so far (Fikáček & Short 2006, Fikáček & Hebauer 2009). Hence, even through the biology of Sacosternum cannot be clearly deduced from the museum specimens, the external morphological characters of Sacosternum do not contradict its possible association with ants derived from the brief label data. The phylogenetic reconstruction performed (Fig. 57), even though generally not very robust, shows at least some well supported clades. Two main clades of Sacosternum are recognized, based mainly of the fundamental differences in the morphology of meso- and metaventrite. The first of these clades currently consists only of two species (Sacosternum sp. A + S. sp. B), both of them known only in females. The second, more speciose clade contains the basal “Sacosternum cruciphallus complex” consisting of few externally very similar species whose positive identification is possible only by examination of the characters of male genitalia. Remaining species of the clade are likely the internal derived forms of the “cruciphallus complex”, exhibiting a slight enlargement of the body, reversal of some elytral and metathoracic characters defining the whole clade and showing a lateral expansion of the prosternal shield. Only the species of the more speciose clade were collected with association with army ants so far (Fig. 57), belonging both to the basal “S. cruciphallus complex” and the more derived clades. Both the species with moderately expanded prosternal shield (S. cruciphallus complex and S. epulum) and with the extremely enlarged one (S. lebbinorum) were collected in association with ants. No data are available for Sacosternum sp. A and S. sp. B. Judging from the extremely enlarged prosternal shield of the Sacosternum sp. A + S. sp. B clade parallel to that of the Sacosternum lebbinorum + S. delta + S. inconnivum clade, the ant-association of the Sacosternum sp. A + S. sp. B clade seems to be however possible. Distributional data of Sacosternum are likely biased by the different collecting effort in different areas (Fig. 56). Six species are known from Costa Rica where a very extensive inventory research has been conducted within last twenty years, resulting in a massive amount of the material of the terrestrial hydrophilids available for the study. Despite this collecting effort, most species are known only from a few specimens from there. The number of species and known localities in whole South America is significantly lower than in Costa Rica, and most of the specimens seem moreover to come from few samples sifted from beneath the Eciton or Labidius bivouacs (two collecting events at two localities in Sacosternum lebbinorum, three collecting events at one locality in S. epulum). In contrast to this virtual rarity, the presented data suggest that Sacosternum is widely distributed in Central America and tropical South America. Known localities of S. lebbinorum and S. garciai moreover allow the possibility that at least some species may be rather widely distributed in this area. The sister-relationships of the species from very distant localities resolved in the phylogenetic analysis (the Peruvian Sacosternum sp. A with the Costa Rican S. sp. B, and the Central American S. inconnivum with the southern Brazilian S. delta) may be caused by the absence of additional species from areas situated inbetween from the tree. This would indicate that additional species of Sacosternum are to be discovered. Sifting of the leaf litter below the ecitonine army ants bivouacs seem to be the promising method for gaining additional specimens as well as more detailed biology data on the genus.

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Acknowledgements We are indebted to all curators of the institutional collections examined for the loan of the material used for this revision, and to M. Archangelsky (Argentina) and an anonymous reviewer for valuable comments on the manuscript. The preparation of this study was supported by a grant of the Ministry of Culture of the Czech Republic MK00002327201, a grant of the Ministry of Education of the Czech Republic MSM0021620828, a grant of Charles University Grant Agency (GAUK) 18307/2007/B-Bio/PrF (all to MF), and by INBio support and US NSF grant #DEB-0816904 to AEZS.

References Fikáček, M. (2009) Taxonomic revision of the New World species of the genus Oosternum Sharp. III. A new species of the O. aequinoctiale species group from Costa Rica. Koleopterologische Rundschau, 79, 179–187. Fikáček, M. (2010) Hydrophilidae: The genus Kanala Balfour-Browne (Coleoptera). In: Jäch, M. A. & Balke, M. (eds.) Water beetles of New Caledonia (part 1). Monographs on Coleoptera 3: 365-394. Fikáček, M. & Hebauer, F. (2009) Taxonomic revision of the New World species of the genus Oosternum Sharp. II. The Oosternum convexum species group. Acta Entomologica Musei Nationalis Pragae, 49, 1, 103–117. Fikáček, M., Hebauer, F. & Hansen, M. (2009) Taxonomic revision of New World species of the genus Oosternum Sharp (Coleoptera: Hydrophilidae: Sphaeridiinae). I. Definition of species groups and revision of the Oosternum aequinoctiale group. Zootaxa, 2054, 1–37. Fikáček, M. & Short, A. E. Z (2006) A revision of the Neotropical genus Motonerus Hansen (Coleoptera: Hydrophilidae: Sphaeridiinae). Zootaxa, 1268, 1–38. Goloboff, P., Farris, J. & Nixon, K. (2008) TNT: a free program for phylogenetic analysis. Cladistics, 24, 774–786. Hansen, M. (1989) New genera of Sphaeridiinae (Coleoptera: Hydrophilidae). Entomologica Scandinavica, 20, 251– 262. Kistner, D.H. (1982) The social insects’ bestiary. In: Hermann, H. R. (ed.) Social Insects. Volume III. Academic Press, New York—London, pp. 1–224. Komarek, A. (2004) Taxonomic revision of Anacaena Thomson, 1859. I. Afrotropical species (Coleoptera, Hydrophilidae). Koleopterologische Rundschau, 74, 303–349. Kovář, I. (1995) Revision of the genera Brumus Muls. and Exochomus Redtb. (Coleoptera, Coccinellidae) of the Palaearctic Region. Part I. Acta Entomologica Musei Nationalis Pragae, 44, 5–124. Nixon, K.C. (2002) WinClada version 1.00.08. Published by the author, Ithaca, New York, USA. Available at http:// www.cladistics.com/about_winc.htm. Tishechkin, A.K. (2009) Discovery of Chlamydopsinae (Insecta, Coleoptera, Histeridae) in Vanuatu with the description of eight new speices from Espiritu Santo Island. Zoosystema, 30, 3, 661–690.

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