The Canadian Entomologist

The Canadian Entomologist Vol. 118

Ottawa, Canada, December 1986

No. 12

TAXONOMIC RESOLUTION OF THREE NEW SPECIES NEAR SZMUHUM VERNUM MACQUART (DIPTERA: SIMULIIDAE)

PETERH. ADLER'and D.C. CURRIE Department of Entomology, University of Alberta, Edmonton, Alberta, Canada T6G 2E3

Abstract

Can. Ent. 118: 1207-1220 (1986)

Three new nearctic species of Simuliidae near Simulium vernurn Macquart are described and illustrated: Simulium craigi n.sp., S. caledonense n.sp., and S. decolletum n.sp. Descriptions of larval polytene chromosomes are included. Notes on biology and distribution are given for each species and larval comparisons are made with three European siblings in the S. vernum complex. On dkcrit et represente sur illustrations trois nouvelles es+ces de Simuliidae uroches de Simulium vernum Macquart: Simulium craigi n.sp., S. caledonense n.sp., et S. decolletum n.sp. On a inclu des descriutions des chromosomes ~olvtknes larvaires. , On fournit des notes sur la biologie et laLrkpartitiongkographique de chaque espkce, et on compare les larves avec celles de trois espkces jumelles d'Europe faisant partie du complexe S. vernum.

.

Introduction Sound phylogenetic and biogeographic schemes for simuliids depend on the resolution of specific identities on a global basis. Cytologists have shown that some populations, recognized under different names in the Palearctic and Nearctic, are conspecific [e.g. Simulium venustum Say and S. truncatum (Lundstrom) (Rothfels et al. 1978)l. Conversely, some populations considered conspecific actually represent distinct species, as in the case of nearctic and palearctic S. vernum Macquart (Brockhouse 1985). As a step toward resolving relationships of the palearctic and nearctic black fly faunas, we have undertaken a partial taxonomic treatment of three species near S. vernum. In North America, the 3. vernum group consists of at least 10 morphospecies. Hunter and Connolly (1986) have presented a cytophylogeny for eight of these species, and Brockhouse (1985) has studied the chromosomes of two other group members (S. bicorne Dorogostaisky, Rubtzov, and Vlasenko, and S . "Yukon"). Cytological studies have established that the morphospecies S. vernum is a complex of more than 12 cytotypes, of which at least 8 are reproductively isolated (Brockhouse 1985) and therefore may be termed sibling species. Four sibling species occur in England, one in Norway, and four or five in North America. Of these, only "Knebworth" of Brockhouse (1985) is presently known to be truly holarctic. In this paper, we describe three species near S. vernum, ali of which are currently known only from the Nearctic. These species are (1) a member of the vernum complex recently resolved chromosomally (Brockhouse, pers. comm.), (2) "Caledon" of the vernum complex (Brockhouse 1984, 1985), and (3) "Yukon" of the vernum group (Brockhouse 1985). Each species is described on the basis of larva, larval polytene chromosomes, pupa, male, and female, following the protocol of Adler and Kim (1985). Larval descriptions are based on material preserved in Carnoy's fixative (one part glacial acetic acid : 'Present address: Department of Entomology, Clemson University, Clemson, South Carolina, USA 296340365.

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three parts 95% ethanol). Measurements and colors of adults are based on dried, pinned material. Morphological terms mainly follow Peterson (1981). Exceptions to this scheme are given in Currie (1986). Chromosomal terms and descriptions are drawn from Brockhouse (1985, pers. comm.). Holotypes, some paratypes, and additional specimens are deposited in the Canadian National Collection, Biosystematics Research Institute, Ottawa. Additional paratypes are deposited in the United States National Museum of Natural History, Washington, and the British Museum (Natural History), London. Chromosomal slide mounts (except types) are deposited in the laboratory of K. Rothfels, University of Toronto.

Simulium craigi n.sp. (Figs. 1 , 4 , 6 , 9 , 13, 17, 19) Larva (final instar). Length 6.0-7.0 mm = 6.5 rnm). Body pale orange-brown to pale greyish brown; intersegmental bands diffuse, poorly defined; ventral tubercles conspicuous, about one-third depth of abdomen at attachment points; posterior abdominal segments dorsally with several simple, pale, barely visible setae. Head capsule (Fig. 1) with cephalic apotome pale yellowish brown; headspots variably distinct, of subequal intensity (first anterolateral and first posterolateral spots sometimes indistinct), delimiting well-defined triangular area of brown pigment of variable intensity (sometimes lacking); eye spots of moderate size, enclosed within small pale area that is surrounded by brown area. Antenna brown dorsally, translucent ventrally; median article paler than proximal and distal articles; apex of median article extending slightly beyond tip of labral-fan stalk; proportions of articles (distal to proximal) 1.O:1.8:1.7. Labral fan with 42-50 (X = 46) primary rays. Hypostomal teeth (Fig. 4) arranged in three groups; median group consisting of relatively large central tooth and smaller (innermost sublateral) tooth on either side; lateral group (on either side of median group) subequal in prominence to median group, consisting of relatively large lateral tooth and smaller (outermost sublateral) tooth; median and lateral groups separated by small median sublateral tooth that is shorter in length than innennost and outermost sublateral teeth; lateral margin of hypostoma with one to two paralateral teeth and two to three lateral serrations per side; hypostoma with three prominent and one to two small, lateral setae per side. Postgenal cleft (Fig. 1) extending one-third to onehalf distance to hypostomal groove, parallel sided or widest at midpoint, well rounded or truncate apically. Venter of head capsule brown, sometimes darker centrally, except for pale yellow triangular area posterior to hypostomal groove; subesophageal ganglion unpigmented to lightly pigmented. Maxillary palpus about 3.3 times as long as basal width. Inner subapical ridge of mandible with four small teeth basal to one large subtriangular tooth. Lateral plate of thoracic proleg lightly to strongly sclerotized, subtriangular, extending almost entire length of apical article. Anterodorsal arms of anal sclerite subequal in length to, and broadly connected to, posteroventral arms. Anal proleg consisting of 9-12 hooks in 66-69 rows. Anal papillae of three compound lobes. Pupa. Length 3.0-4.0 mm (X = 3.6 mm). Gill (Fig. 6) slightly longer than pupa, consisting of four filaments that gently curve ventrally and run parallel to substrate; base very short, giving rise to two petioles that diverge vertically at an angle of 30 + 5" (X + SD); dorsal petiole up to twice as thick as, at least one-third the length of, and usually distinctly lateral to ventral petiole; dorsal and ventral petioles giving rise to two filaments usually bifurcating in horizontal plane; filaments long, thin, tapering, with numerous moderately deep furrows; surface sculpture of base with numerous rounded wrinkles. Thorax anterior to wing base dorsally with many conspicuous, rounded, strongly raised, darkened nodules (Fig. 9), contrasting strongly with lighter surrounding cuticle; trichomes simple, very slender, pale, slightly curved, with seven or (usually) eight on each side of thorax. Tergite 1 bare; tergite 2 with irregular row of fine, posteriorly positioned, anteriorly directed setae on either side of midline, numbering three to six on each side and with additional one or

(x

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I

0.25 rnrn

bjJ -

u

0.25 mrn

*

3

FIGS. 1-5. 1 , Simulium craigi n.sp., head capsule (dorsal, ventral); 2, S. caledonense n.sp., head capsule; 3, S. decolletum n.sp., head capsule; 4, S. craigi n.sp., hypostomal teeth; 5 , S.caledonense n.sp., hypostomal teeth.

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two very small, fine setae anterolaterally; tergites 3 and 4 each posteriorly with four anteriorly directed hooks on either side of midline (total eight per tergite) and usually with one fine seta anterior to lateralmost hook on either side of tergite; tergites 5-8 (occasionally 9) each with row of fine, closely set, posteriorly directed spines along anterior margin on either side of midline; tergite 9 with pair of darkened, short, stout, slightly curving, dorsally directed terminal spines; pleural membrane of segments 2-4 (occasionally 5) with one to three (average two) minute setae. Sternite 3 bare, or with pair of minute, anteriorly directed setae; sternite 4 with two to six minute, irregularly positioned, anteriorly directed setae; sternite 5 posteriorly with two pairs of small, often multifid hooks side by side and rather close to midline, usually with four minute setae (one seta anterolateral to lateral hook on each side, and one seta lateral to lateral hook on each side); sternites 6 and 7 posteriorly with four small, often multifid hooks (two rather close together on either side of midline, and two more laterally), and with two to six setae; sternites 8 and 9 bare. Head projecting downward, not easily visible dorsally, with many nodules as on thorax; antennal sheath of female extending to posterior margin of head; antennal sheath of male extending about one-half distance to posterior margin of head. Cocoon well formed, with anterodorsal projection broad and accounting for about 17.5-26.9% ( x = 21.9%) total cocoon length (in lateral view); anterior margin and anterodorsal projection strongly reinforced. Female. Generally brown with grey pruinosity and pale golden pile. Length: body, 2.73.1 mm (2 = 2.9 mm); wing, 2.9-3.9 mm ( 2 = 3.3 mm). Frons at vertex about two times broader than at narrowest point, about one-quarter width of head, sparsely covered with decumbent, pale golden pile. Clypeus slightly longer than wide, with sparse, pale golden pile. Occiput with long, pale golden pile reaching posterior margin of eye; postocular setae black. Antenna with fine, silver pubescence; first flagellomere longest; pedicel and scape brown to light brown; flagellum dark brown. Mandible with 35-38 serrations. Lacinia with 2 6 2 6 retrorse teeth. Palpus dark brown, with stout, pale golden setae; palpomere V 1.5-2.0 times as long as 111. Sensory vesicle located subcentrally, occupying one-half of palpomere 111; neck long, thin, arising near anterodorsal margin, opening to exterior through rounded, slightly expanded mouth. Median proximal space of cibarium U-shaped. Postpronotum dark brown; pile long, erect, pale golden. Scutum dark brown, humeral angles brown; pile recumbent, pale golden centrally, silver anteriorly and laterally in most specimens. Scutellum brown, with long, golden pile and a few black or black-tipped setae. Postnotum brownish black. Anepisternum and katepisternum dark brown; membrane and mesepimeron lighter brown; mesepimeral tuft of long, golden setae. Wing veins pale yellowish brown; setae on stem vein and costal base golden and dark mixed; setae on other veins primarily dark; subcosta setose ventrally; fringe of calypter and alar lobe pale golden. Halter yellowish brown to tan, with golden pile. Coxae, tarsi, and apices of femora and tibiae brown, remainder of legs light brown; pile on coxae silver, pale golden on femora and tibiae, mainly dark on tarsi; hind basitarsus 5.8-7.0 times as long as broad; calcipala and pedisulcus well developed; each claw with large, basal, thumb-like lobe. Abdominal sclerites brown; pile sparse, pale golden; additional sparse, long, black setae on tergites 8-9; membranous areas grey to tan, with sparse, mixed black and pale golden pile. Basal fringe of very long, pale golden pile. Anal lobe subquadrate in lateral view, with rounded or pointed posterodorsal extension and small anteroventral nipple. Cercus subrectangular to subtriangular, posterior margin well rounded to nearly straight. Hypogynial lobes subtriangular, bluntly rounded posteriorly, space between them narrow. Genital fork (Fig. 19) with stem moderately long and sclerotized, especially apically; lateral arms considerably broadened basally, expanding posteromedially into well-developed processes with rounded angles, forming suboval space in region of bifurcation. Spermatheca small, longer than broad, with surficial pattern of subequal polygons.

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Male. Generally velvety black with grey pruinosity and golden pile. Length: body, 2.73.5 mm (x = 3.0 mm); wing, 2.5-3.0 mm (2? = 2.8 mm). Frons and clypeus with erect, brown pile. Occiput with long, brown to golden brown pile. Antenna dark brown, with fine, light brown pile. Palpus dark brown, with dark brown pile; palpomere V twice as long as palpomere 111. Sensory vesicle subspherical, about one-sixth to one-seventh length of its segment; neck long, slender, opening to exterior through rounded mouth. Postpronotum brown, with golden pile. Scutum black, with recumbent, golden pile; anterior pits of scutum reddish brown. Scutellum brown with golden brown pile. Postnotum brownish black. Anepisternum dark brown, lighter posteriorly; katepisternum blackish brown; membrane and mesepimeron brown; mesepimeral tuft of long, brown to golden pile. Wing veins pale yellowish brown. Setae on stem vein golden brown; setae on costal base dark brown; setae on other veins golden brown; fringe of calypter and alar lobe golden brown. Halter tan with dark brown pile. Legs dark brown, midsection of femora and tibiae brown to light brown; pile golden to brown. Hind basitarsus 4.0-4.5 times as long as broad. Abdominal tergites dark brown, with golden brown pile; membranous areas grey laterally, tan to greyish tan ventrally, with long, golden brown setae laterally on segments 3 and 4; sternites brown with long, brown pile. Basal fringe of very long, brown to golden brown pile. Terminalia as in Figure 13. Gonocoxite slightly longer than broad. Gonostylus about one-half as long as gonocoxite, about twice as long as breadth at midpoint, expanded apically into flattened, subtriangular, medially directed flange bearing one apical spine. Ventral plate in ventral view subrectangular, 2.5-3.0 times as broad as long, moderately tapering posteriorly, with posterolateral comers well rounded and posterior margin rounded or truncate, or with very small, medial concavity; anterior margin slightly concave to slightly convex; arms rather straight, diverging slightly, tips of arms sometimes curved inward; lip in terminal view short, broad; stem of median sclerite long, forked about onethird to one-half distance from distal end; dorsal plate (Fig. 17) well sclerotized, with broad collar-like base, suborbicular distally; paramere in lateral view moderately narrow basally, broadening medially, then narrowing distally and bearing one long, slender, strongly sclerotized spine-like process. Chromosomes. n = 3; chromosomes I, 11, and IIIS standard for S. vernum group; IIIL with inversion IIIL-3 (limits 87B-91C3); B chromosomes often present; sex chromosomes unresolved. Remarks. All life stages of S. craigi are somewhat intermediate between those of S. caledonense n.sp. and S. decolletum n.sp. Simulium craigi can be distinguished from these two species by the headspot pattern, shape of the postgenal cleft, divergence angle of the dorsal and ventral petioles of the pupal gill, strongly raised nodules on the pupal head and thorax anterior to the scutellum, width to length ratio (2.5-3.0) of the ventral plate (in ventral view), and strong infilling of the genital fork at the point of bifurcation. Of these three new species, larvae of S. craigi are morphologically closest (e.g. in setal vestiture, head pattern, and shape of the postgenal cleft) to those of the European S. vernum sibling species that we have examined ["Dorset IIS-l", "Knebworth", and "Lymington" of Brockhouse (1985)l. Larvae of "Dorset IIS-1" (sample size = 8), however, are paler and have a strong posteromedian headspot contrasting with weaker remaining headspots. Larvae of "Knebworth" (sample size = 6) have distinct headspots but lack an obvious encompassing fulvous area; setal vestiture of the posterodorsal abdominal region is moderately developed. Larvae of "Lymington" also appear to have distinct headspots and an inconspicuous fulvous area, although the 14 Feulgen-stained larvae that we examined were in poor condition. Simulium craigi differs most conspicuously from these three European

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THE CANADIAN P.NTOMOLOGIST

Table 1. Numbers of immatures of three species near Simulium vernum collected 3.1 km west of Obed on Highway 16 (53"33'N, 117"14'W), Alberta

S . craigi

Larvae 8 June 11 June 15 June 27 June

1985 1984 1984 1984

22 70 37 1

S . caledonense Pu~ae 47 48 50 0

Larvae

78 34 163 40

Pu~ae 5 3 8 22

S . decolletum

Larvae

Pu~ae

0 0 0 0

0 1 0 0

siblings in possessing hypostomal teeth arranged in three distinct aggregates. Chromosomal characteristics place S. craigi in the "Caledon" - "Nipigon" lineage within the S. vernum complex (Brockhouse 1985, pers. cornrn.). To date, S. craigi is known only from the Foothill Ecoregion [as defined by Currie (1986)l of Alberta. Immatures of S. craigi were collected from streams a metre or less in width that issued from bogs or springs and ranged in temperature from 15 to 22.5"C, in pH from 8.00 to 8.12, and in conductivity from 35 to 40 pS cm-I. Pupation occurred most often on the undersurfaces of stones. Larvae and pupae were found from June to August in association with S. caledonense n.sp. and S. decolletum n.sp. Two of five sites in Alberta yielded all three species, but repeat collections at one of these sites indicated that population cycles were out of phase (Table 1). Species most commonly collected with S. craigi were Prosimulium formosum Shewell and S. tuberosum (Lundstrom) cytospecies FGH. Two larvae of S. craigi (n = 165) were infected with microsporidian protozoans and three with mermithid nematodes.

Etymology. This species is named in honor of Douglas A. Craig, Department of Entomology, University of Alberta, in recognition of his contributionsto the study of simuliids. Type material. Holotype: I3 with pupal exuviae (pinned), ALBERTA: 3.1 km west of Obed on Highway 16 (53"33'N, 117"14'W), 11 June 1984, P.H. Adler and D. C. Cume. Allotype: 9 with pupal exuviae (pinned), same data as holotype. Paratypes: 9 6 8, 14 9 Q with pupal exuviae (pinned), 70 larvae, 23 pupae (in alcohol), same data as holotype; 138 13, 7 9 Q with exuviae (pinned), 37 larvae, 30 pupae, 4 pupal exuviae (in alcohol), same location as holotype, 15 June 1984, P.H. Adler and D.C. Currie; 22 larvae, 47 pupae (in alcohol), same location as holotype, 8 June 1985, D.C. Currie; 2 larvae (in alcohol), 2 chromosome preparations (by Brockhouse), ALBERTA: 3.2 km east of Obed Summit on Highway 16 (53"31rN, 117"17'W), 8 June 1985, D.C. Currie; 16 ,6 9 9 with pupal exuviae (pinned), 5 larvae, 1 pupal exuviae (in alcohol), ALBERTA: 1 km northwest of Edith Lake, Swan Hills (54"48'N, 115"23'W), 2 August 1984, P.H. Adler and D.C. Currie. Additional specimens examined. ALBERTA: 3.1 km west of Obed on Highway 16 (53"33'N, 117"14'W), 27 June 1984, P.H. Adler (1 larva); 3.2 km east of Obed Summit on Highway 16 (53"31tN, 117"17'W), 15 June 1984, P.H. Adler (20 larvae), and 8 June 1985, D.C. Currie (8 larvae). Simulium caledonense n.sp. (Figs. 2 , 5 , 7 , 10, 14, 16, 18) Eusimulium latipes "Ste. Rose": Landau, unpublished, in Dunbar, 1962: 31, chromosomes. Eusimulium vernum "Caledon": Brockhouse, 1984: 35, chromosomes. Eusimulium vernum ' 'Caledon" : Brockhouse, 1985: 2 152, chromosomes. Simulium (Nevermannia) vernum cytospecies Caledon: Adler and Kim, 1986: 32, larva, pupa.

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FIGS.6-12. 6, Simulium craigi n.sp., pupal gill (lateral), bar = 100 pm; 7, S. caledonense n.sp., pupal gill, bar = 100 pm; 8, S. decolletum n.sp., pupal gill, bar = 100 pm; 9, S. craigi n.sp., microsculpture of thoracic dorsum, bar = 40 pm; 10, S. caledonense n.sp., microsculpture of thoracic dorsurn, bar = 40 pm; 11, S. decolletum n.sp., microsculpture of thoracic dorsum, bar = 40 pm; 12, S. decolletum n.sp., microsculpture of thoracic dorsum, bar = 10 pm.

(x

Larva (final instar). Length 5.3-6.2 mm = 5.8 mm). Body orange-brown, diffusely banded; ventral tubercles conspicuous, about one-third depth of abdomen at attachment points; posterior three to four abdominal segments dorsally with many short, dark, simple setae. Head capsule (Fig. 2) pale yellowish brown dorsally; headspots dark brown, encompassed, at least centrally, with brown pigment of variable intensity; anterolateral headspots strong, distinct, separate, other headspots diffuse or distinct; eye spots of moderate size, enclosed within small, pale yellow area that is surrounded by brown area. Antenna pale yellowish brown dorsally, translucent ventrally; apex of median article reaching end of

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labral-fan stalk; proportions of articles (distal to proximal) 1.O: 1.5:1.3. Labral fan with 47-56 (X= 52) primary rays. Hypostomal teeth (Fig. 5) with median tooth and lateral teeth relatively large and subequal in length and prominence; sublateral teeth variously smaller and subequal in length, not strongly associated with either median or lateral teeth; lateral margin of hypostoma with two paralateral teeth and two to three lateral serrations per side; hypostoma with three prominent and one to two small, lateral setae per side. Postgenal cleft (Fig. 2) about twice as long as wide, extending one-half distance to hypostomal groove, widest at midpoint, well rounded apically, surrounded by brown pigment that extends anteromedially in one thick band or (more commonly) in two diffuse branches to hypostomal groove; subesophageal ganglion unpigmented. Maxillary palpus 2.9-3.3 times as long as basal width. Inner subapical ridge of mandible with two to three small teeth basal to one large, subtriangular tooth. Lateral plate of thoracic proleg lightly to moderately sclerotized, subtriangular, extending almost entire length of apical article. Anterodorsal arms of anal sclerite subequal in length to and broadly connected to posteroventral arms. Anal proleg consisting of 10-13 hooks in 61-68 rows. Anal papillae of three compound lobes. Pupa. Length 2.6-3.3 mm (X = 3.0 mm). Gill (Fig. 7) slightly longer than pupa, consisting of four filaments that gently curve ventrally and run parallel to substrate; base very short, giving rise to two petioles that diverge vertically at an angle of 67 + 16"; ventral petiole subequal in thickness to, up to twice as long as, and (in dorsal view) subparallel to dorsal petiole; ventral petiole giving rise to two filaments bifurcating in horizontal or vertical plane; dorsal petiole giving rise to two filaments usually bifurcating in vertical plane; filaments long, thin, tapering, with numerous shallow furrows; surface sculpture of base not well differentiated. Anterior portion of thorax dorsally with numerous rounded, moderately raised nodules (Fig. 10); thoracic and abdominal chaetotaxy as in S. craigi n.sp. except for subtle and irregular reduction of some setae. Head projecting downward, not easily visible dorsally, with nodules as on thorax; antennal sheath of female extending to or slightly beyond posterior margin of head; antennal sheath of male extending about one-half distance to posterior margin of head. Cocoon well formed, with anterdorsal projection narrow and accounting for about 22.5-31.6% 27.7%) total cocoon length (in lateral view); anterior margin and medial region of anterodorsal projection reinforced. Female. Not differing from S. craigi n.sp. except as follows. Length: body, 2.4-2.7 mm (X = 2.6 mm); wing, 2.3-2.9 mm (X = 2.7 mm). Pile generally more silvery, especially on clypeus, frons, calypter, alar lobe, basal fringe, and sometimes scutum. Setae on stem vein and costal base darker. Lacinia with up to 29 retrorse teeth. Cercus often as long as broad. Lateral arms of genital fork (Fig. 18) rather narrow basally, forming subquandrangular space in region of bifurcation, posteromedial angles usually acute. Spermatheca of moderate size. Male. Not differing from S. craigi n.sp. except as follows. Length: body, 2.4-3.2 rnm = 2.7 mm); wing, 2.2-3.0 mm (X = 2.6 mm). Hind basitarsus 3.6-5.0 times as long as broad. Terrninalia as in Figure 14. Gonostylus with one to two spines on apex of flange. Ventral plate in ventral view about two times as broad as long, tapering posteriorly, with posterior margin rounded or truncate, entire; arms subparallel or bowed, with tips curving inward; lip in terminal view broader and less prominent; dorsal plate (Fig. 16) not as strongly sclerotized nor as broad distally. Chromosomes. n = 3; chromosome I standard for S. vernum group; IIS with overlapping inversions 11s-4,5 (limits 52C-5 1C2 and 48B3-52B4), standard sequence floating in some populations; IIL with fixed inversions IIL-1 2 (limits 60A3-64 and 70B-73A1); IIIS with 111s-1 (limits 75C2-80A), rarely floating; IIIL with sex inversions as follows: X chromosome with inversions IIIL- 1, 2 3 , 4 (limits 97-92C, 94B-98, 87B-91C3, 87C-

(x=

(x

+

+

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FIGS.13-17. Male terminalla: 13, Simulium craigi n.sp. (ventral with left gonocoxite and gonostylus removed); 14, S. caledonense n.sp.; 15, S. decolletum n.sp.; 16, S. caledonense n.sp., dorsal plate (dorsal); 17, S. craigi n.sp., dorsal plate.

+

9 1C3, respectively), Y chromosome with inversions IIIL- 1, 2 3 , 4 plus inversions IIIL5 andlor 6.7 (limits 91C-94C andlor 86C-88A/88A-89A), sex exceptions frequent; B chromosomes often present. Remarks. Simulium caledonense is readily distinguished in the larval stage from S. craigi n.sp., S. decolletum n.sp., and the three European S. vernum siblings we have examined ("Dorset 11s-1 ", "Lymington", and "Knebworth"), principally by the head pattern, shape of the postgenal cleft, and the more well-developed setal vestiture of the posterodorsal

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abdominal region. Simulium caledonense is also chromosomally more remote from the standard S. vernum arrangement than these species (Brockhouse 1985). The critical issue, however, is the degree of morphological differentiation from sympatric and syntopic sibling species, "Nipigon" and "Eastmain" of Brockhouse (1985), and possible sibling species, "Labrador", "Cypress Hills", and "Gothic" also of Brockhouse (1985). Unfortunately, no material was available for comparison. Chromosomally, S. caledonense can be distinguished from other members of the S. vernum complex by fixed inversion IIIS1; however, several members of the S. vernum group, such as S. pugetense (Dyar and Shannon) and S. quebecense Twinn, have a similar inversion that reverses the position and orientation of the "blister" (Hunter and Connolly 1986). Pupae and adults can be distinguished from those of S. craigi n.sp. and S. decolletum n.sp. by the wide divergence angle of the dorsal and ventral petioles of the pupal gill, width to length ratio (2.0) of the ventral plate (in ventral view), moderately sclerotized dorsal plate, and subquadrangular space in the region of bifurcation of the genital fork. We have found immatures of S. caledonense in spring- or bog-fed streams no more than a metre in width. These streams ranged in temperature from 12 to 22.5"C, in pH from 8.00 to 8.12, and in conductivity from 35 to 40 p,S cm-I. Larvae occurred on stones or trailing vegetation, and pupated most frequently on the undersurfaces of stones. Simulium caledonense is found from April in Pennsylvania through August in Alberta. In Labrador, at one site, larvae were collected in both May and August, indicating that at least two generations occur in some areas (Brockhouse 1985). Two larvae from Alberta (n = 337) were parasitized by mennithid nematodes. Simulium caledonense is known from Labrador, Quebec, Ontario, Manitoba (Brockhouse 1985), Alberta, and Pennsylvania.

Etymology. The specific name is derived from "Caledon", the cytological designation (after Caledon, Ontario) for this species (Brockhouse 1985). Type material. Holotype: I3 with pupal exuviae (pinned), ALBERTA: 3.1 km west of Obed on Highway 16 (53"33'N, 117"14'W), 15 June 1984, P.H. Adler and D.C. Currie. Allotype: 9 with pupal exuviae (pinned), same data as holotype, 27 June 1984. Paratypes: 34 larvae, 3 pupae (in alcohol), same location as holotype, 11 June 1984, P.H. Adler and D.C. Currie; 4 8 8 with pupal exuviae (pinned), 163 larvae, 3 pupae (in alcohol), same location as holotype, 15 June 1984, P.H. Adler and D.C. Cume; 8 I3 8 , 8 0 9 with pupal exuviae (pinned), 40 larvae, 4 pupae, 2 pupal exuviae, 1 6 (in alcohol), same location as holotype, 27 June 1984, P.H. Adler; 78 larvae, 5 pupae (in alcohol), same location as holotype, 8 June 1985, D.C. Cume. Additional specimens examined. PENNSYLVANIA: Pike County, stream paralleling Rt. 209, mile marker 12, south of Dingmans Ferry (41°13'N, 74O5 1'W), 12 May 1984, P.H. Adler and C.R. Loerch [(8 larvae, 6 chromosomal preparations by Brockhouse (1985)l; ALBERTA: below beaver dam, Highway 22, about 10 km south of Buck Creek (53"02'N, 114"52'W), 1 June 1982, D.C. Cume (9 larvae); Cottonwood Creek, Jasper National Park, 1.5 km north of Jasper (54"54'N, 118"05'W), 13 June 1963, D.M. Wood (1 larva); 1 km northwest of Edith Lake, Swan Hills (54"48'N, 115"23'W), 2 August 1984, P.H. Adler and D.C. Cume [4 larvae, 4 chromosome preparations by Brockhouse (1985)l. Simulium decolletum n.sp. (Figs. 3, 8, 11, 12, 15, 20) Eusimulium X : Choate, 1984: 52, chromosomes. Eusimulium "Yukon": Brockhouse, 1984: 43, chromosomes. Eusimulium "Yukon": Brockhouse, 1985: 2154, chromosomes.

(x

Larva (final instar). Length 5.7-7.0 mm = 6.4 rnrn). Body orange-brown to pale greyish brown, diffusely banded; ventral tubercles conspicuous, one-third to one-half depth

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FIGS.18-20. Female genital fork (ventral): 18, S. caledonense n.sp.; 19, S . craigi n.sp.; 20, S.decolletum n.sp.

of abdomen at attachment points; posterior abdominal segments dorsally with several pale, simple, barely visible setae. Head capsule (Fig. 3) almost entirely yellowish brown; headspots brown, contrasting with paler head capsule, subequal in intensity, not distinctly encompassed with darker pigment except sometimes posteriorly; first anterolateral and first posterolateral spots sometimes weak; eye spots small to moderate in size; line over eye spots thin, brown; pigmented area anteroventral to eye spots small or absent. Antenna pale yellowish brown dorsally, translucent ventrally; apex of median article extending slightly beyond end of labral-fan stalk; proportions of articles (distal to proximal) 49) primary rays. Hypostomal teeth arranged in 1.O: 1.7:1.5. Labral fan with 43-57 three distinct clusters, as in Simulium craigi n.sp.; lateral margin of hypostoma with two paralateral teeth and two to three lateral serrations per side; hypostoma with three prominent and zero to four small lateral setae per side. Postgenal cleft (Fig. 3) about as wide as long, parallel sided or widest anterior to midpoint, gently rounded to truncate apically, extending about one-third distance to hypostomal groove, at most weakly surrounded by pale brown pigment; subesophageal ganglion unpigmented. Maxillary palpus about 2.5 times as long as basal width. Inner subapical ridge of mandible with two to three small teeth basal to one large, subtriangular tooth. Lateral plate of thoracic proleg lightly to moderately sclerotized, subtriangular, extending almost entire length of apical article. Anterodorsal arms of anal sclerite slightly shorter than and broadly connected to posteroventral arms. Anal proleg consisting of 11-14 hooks in 73-74 rows. Anal papillae of three compound lobes.

(x=

(x

Pupa. Length 3.2-3.6 mm = 3.4 mm). Gill (Fig. 8) longer than pupa, consisting of four filaments that curve ventrally and run parallel to substrate; base short, giving rise to two bifurcate petioles of subequal length that diverge vertically at an angle of less than 35"; petioles somewhat divergent horizontally (ventral petiole more medial), running parallel in vertical plane; dorsal petiole up to twice as thick as ventral petiole; filaments long, thin, tapering, with numerous shallow furrows; surface sculpture of base pustulate. Thorax anterior to postscutellum with abundant dark, strongly raised, rounded nodules (Figs. 11, 12); cuticle, including that of nodules, with minute granules; trichomes simple, very slender, curving, eight per side. Tergite 1 with one to two pairs of minute setae; tergite 2 posteriorly with four anteriorly directed setae on each side (total eight) and with up to five additional anterolateral setae; tergites 3 and 4 each posteriorly with eight anteriorly directed hooks (four hooks each on either side of midline) and with one seta anterior to lateralmost hooks on each side; tergites 5-8 anteriorly with row of fine, closely set, posteriorly directed spines on each side of midline (spines becoming progressively more pronounced from segment 5 through 8); tergite 9 with pair of very short, lightly sclerotized, dorsally directed

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terminal spines. Pleural membrane of segments 3 and 4 with two to three minute setae. Sternite 4 with three to four small setae on each side of midline; sternite 5 with two pairs of small, often multifid hooks side by side on posterior margin of sternite and rather close to midline; sternites 6 and 7 posteriorly with four small, often multifid hooks (two rather close together on either side of midline, and two more lateral), and with one seta between hooks on each side and another anterolateral to lateralmost hook; sternites 8 and 9 bare. Head sloping forward, entirely visible dorsally, with granulate nodules as on thorax; antennal sheath of female extending to posterior margin of head; antenna1 sheath of male extending slightly over one-half distance to posterior margin of head. Cocoon oval from dorsal perspective, splaying laterally, with a semicircular excavation anteriorly that exposes head and much of thorax; anterior margin reinforced, without median projection. Female. (Based on one pharate specimen dissected from pupa; colors not determinable.) Not differing structurally from S. craigi n.sp. except as follows. Lateral arms of genital fork (Fig. 20) less broad basally, with less infilling at point of bifurcation and with posteromedial areas less developed. Male. Not differing from S. craigi n.sp. except as follows. Length: body, 2.5 mm; wing, 2.8 mm. Hind basitarsus 3.7 times as long as broad. Terminalia as in Figure 15. Ventral plate in ventral view subrectangular, about two times as broad as long, not obviously tapering posteriorly, with anterior margin nearly straight or slightly concave and posterior margin with distinct, medial notch; arms long, well sclerotized, slightly bowed, with tips curving inward; ventral lip in terminal view slightly longer, more pronounced; dorsal plate not as broad distally. Chromosomes. n = 3; chromosomes I, 11, and IIIS standard for S. vernum group; IIIL with fixed inversion IIIL-29 (limits 90B-91C3); sex chromosomes undifferentiated (X,,Y,,); floating inversions common; B chromosomes absent. Remarks. The similarity of all life stages of S. decolletum to those of S. pugetense (Dyar and Shannon) necessitated examination of the holotype (6)of S. pugetense, itself a complex of several sibling species (Hunter and Connolly 1986). The posteroventral comers of the ventral plate of S. decolletum are more rounded, the hirsute nipple is not strongly developed, and the arms of the ventral plate are straighter, compared with the holotype of S. pugetense. Larvae of S. decolletum are most readily distinguished from those of S. pugetense by the presence of compound, not simple, anal papillae. Simulium decolletum is distinguished from S. craigi n.sp. and S. caledonense n.sp. by the truncate postgenal cleft, excavated anterior margin of the cocoon, inclined pupal head, granulate nodules on the pupal thorax, distinct medial notch of the ventral plate, and moderate infilling of the genital fork at the point of bifurcation. Fixed inversion IIIL-29 is the diagnostic chromosomal feature. Simulium decolletum bears a manifest resemblance to S. truncatum (Rivosecchi and Cardinali) of Italy and southeastern France. [Simulium truncatum (R. & C.) is a junior secondary homonym of S. truncatum Lundstrijm.] We have not seen material of S. truncatum (R. & C.) for direct comparisons. However, our comparisons of S. decolletum with drawings of S. truncatum (R. & C.) in Dorier and Grenier (1961) and in Rivosecchi (1978) reveal three obvious differences: (1) distinct infuscation occurs in the area of the larval headspots of S. truncatum (R. & C.) but not of S. decolletum; (2) the postgenal cleft extends slightly more than one-half the distance to the hypostomal groove in S. truncatum (R. & C.), but only one-third that distance in S. decolletum; (3) the most striking feature is the gradual anterior slope of the pupal head of S. decolletum versus the abrupt anterior curvature in S. truncatum (R. & C.); this difference renders the pupal head entirely visible from above in S. decolletum but scarcely so in S. truncatum (R. & C.).

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Pupae of S. decolletum from Alberta and the Yukon had an amorphous covering on the head and thorax. Elemental analysis with a KEVEX Micro-X 7000 analytical energydispersive spectrometer revealed that the material was organic. Washings in ammonia and prolonged sonication removed this material. We do not know if this flocculent covering is characteristic of all S. decolletum pupae, nor do we know its origin. Immatures of S. decolletum have been collected in the Foothill Ecoregion of Alberta from June to August. All streams from which we took larvae and pupae were a metre or less in width and spring- or bog-fed. Immatures were collected within a temperature range of 15-19"C, a pH range of 8.00-8.12, and at a conductivity of 40 p,S cm-I. Larval densities did not exceed 65 m-2 at any Alberta collection site. One larva from Alberta (n = 39) was infected with the fungus Coelomycidium simulii Debaisieux. Simulium decolletum is also known from Alaska (Brockhouse 1985) and the Yukon.

Etymology. The specific name for this species was inspired by Klaus Rothfels and Roger Crosskey, who informally dubbed it Simulium "dtcolletC", in reference to the excavated anterior margin of the pupal cocoon, exposing much of the thorax. Type material. Holotype: 8 with pupal exuviae (pinned), ALBERTA: 1 km northwest of Edith Lake, Swan Hills (54"4gtN, 115"23'W), 2 August 1984, P.H. Adler and D.C. Currie. Paratypes: 1 P (pharate, in glycerin), ALBERTA: 3.1 km west of Obed on Highway 16 (53"33'N, 117"14'W), 11 June 1984, P.H. Adler and D.C. Cume; 2 larvae [9 chromosome preparations from this collection examined by Brockhouse (1985), but not included as paratypes], 2 pupae, 3 pupal exuviae (in alcohol), ALBERTA: 3.2 km east of Obed Summit on Highway 16 (53"31tN, 117"17'W), 15 June 1984, P.H. Adler; 4 larvae [7 chromosome preparations from this collection examined by Brockhouse (1985), but not included as paratypesj, 3 pupal exuviae (in alcohol), same data as holotype; 56 larvae, 86 pupae (in alcohol), YUKON: stream on Dempster Highway, km 18, Ogilvie Mts. (64"06'N, 138'3 1'W), 18 July 1982, R.W. Crosskey; 3 8 8 with pupal exuviae (pinned), 2 larvae, 1 pupa (in alcohol), YUKON: stream on Dempster Highway, km 92, Ogilvie Mts. (64"37'N, 138"20tW), 19 July 1982, R.W. Crosskey; 12 pupae (in alcohol), YUKON: stream on Dempster Highway, km 222, Ogilvie Mts. (65"32'N, 138"15'W), 15 July 1982, R.W. Crosskey. Additional specimens examined. ALBERTA: 1.2 km northwest of Edith Lake, Swan Hills (54"48'N, 115"23'W), 2 August 1984, P.H Adler and D.C. Currie (9 larvae). Acknowledgments We thank C.L. Brockhouse and K.H. Rothfels, University of Toronto, for their close cooperation, loan of chromosomal maps and larvae, and resolution of several chromosomal matters; R.W. Crosskey, British Museum (Natural History), for loaning specimens of S. decolletum and for bringing to our attention S. truncatum (R. & C.) and associated nomenclatural problems; B.V. Peterson, Systematic Entomology Laboratory, Washington, DC, for loaning the holotype of S. pugetense; D. Hollingdale for rendering the illustrations; and G. Braybrook for assistance with scanning electron microscopy. We also thank the following individuals who commented on the manuscript: C .R .L. Adler, D. A. Craig, R.W. Crosskey, and D.M. Wood. We extend special thanks to D.A. Craig for his support of this research (Natural Sciences and Engineering Research Council of Canada grant A-5753 to Craig). References Adler, P.H., and K.C. Kim. 1985. Taxonomy of black fly sibling species: two new species in the Prosimulium mixtum group (Diptera: Simuliidae). Ann. ent. Soc. Am. 78: 4149. -1986. The black flies (Simuliidae, Diptera) of Pennsylvania: bionomics, taxonomy, and distribution. Pa. State Univ. Agric. Exp. Sta. Bull. 856. 88 pp.

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Brockhouse, C.L. 1984. Sibling species and sex chromosomes in Eusimulium vernum (Diptera: Simuliidae). M.Sc. thesis, Univ. Toronto, Ontario. 66 pp. 1985. Sibling species and sex chromosomesin Eusimulium vernum (Diptera: Simuliidae). Can. J. Zool. 63: 2145-2161. Choate, L.A. 1984. A cytological description of Eusimulium vernum, E. X , and the E. pugetense complex (Diptera: Simuliidae) in Alaska. M.Sc. thesis, Univ. Alaska, Fairbanks, Alaska. 122 pp. Currie, D.C. 1986. An annotated list of and keys to the immature black flies of Alberta (Diptera: Simuliidae). Mem. ent. Soc. Can. 134. 90 pp. Dorier, A,, and P. Grenier. 1961. Description de deux formes nouvelles de Simulies: Simulium carthusiense f. brevicaulis et Simulium carthusiense f. truncata. Trav. Lab. Hydrobiol. Pisc. 52(53): 93-100. Dunbar, R.W. 1962. Cytotaxonomic studies in Simuliidae. Ph.D. thesis, Univ. Toronto, Ontario. 101 pp. Hunter, F.F., and V. Connolly. 1986. A cytotaxonomic investigation of seven species in the Eusimulium vernum group (Diptera: Simuliidae). Can. J. Zool. 64: 296-31 1. Peterson, B.V. 1981. Simuliidae. pp. 355-391 in McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth, and D.M. Wood (Coords.), Manual of Nearctic Diptera, Vol. I. Res. Br., Agric. Can. (Ottawa) Monograph 27. 674 pp. Rivosecchi, L. 1978. Simuliidae: Diptera, Nematocera. Fauna Ital. 13: 1-529. (In Italian.) Rothfels, K., R. Feraday, and A. Kaneps. 1978. A cytological description of sibling species of Simulium venustum and S. verecundum with standard maps for the subgenus Simulium Davies (Diptera). Can. J. Zool. 56: 1110-1128. (Date received: 1985 12 03; date revision received: 1986 07 02; date accepted: 1986 07 03)