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PROC. ENTOMOL. SOC. WASH. 115(2), 2013, pp.
ESTABLISHMENT OF THE PALEARCTIC HETEROGASTER URTICAE (F.) (HEMIPTERA: LYGAEOIDEA: HETEROGASTRIDAE) IN NORTH AMERICA, WITH NEW BRITISH COLUMBIA RECORDS OF THE NATIVE H. BEHRENSII (UHLER) A. G. WHEELER, JR.
AND
E. RICHARD HOEBEKE
(AGW) School of Agricultural, Forest, and Environmental Sciences, Clemson University, Clemson, South Carolina 29634-0310, U.S.A. (e-mail: awhlr@clemson. edu); (ERH) Georgia Museum of Natural History and Department of Entomology, University of Georgia, Athens, Georgia 30602, U.S.A. (e-mail:
[email protected])
Abstract.—Stinging nettle (Urtica dioica L.; Urticaceae), a Holarctic perennial herb, is a host plant of two lygaeoids of the family Heterogastridae: Heterogaster urticae (F.) in the Palearctic and H. behrensii (Uhler) in the Nearctic Region. We give the first published North American records (other than port-of-entry interceptions) of H. urticae, based on fieldwork in British Columbia in 2010 and 2011. We also give new distribution records for H. behrensii, a species of special concern in the province; it previously was known in Canada only from one site in British Columbia. Morphological characters are provided to distinguish the species. Both heterogastrids were collected from stinging nettle in British Columbia’s Lower Fraser Valley and on Vancouver Island; H. urticae also was taken in the Vancouver Metro Area. The species were syntopic in two nettle colonies. We suggest that the heterogastrids’syntopy provides an opportunity to determine whether the adventive H. urticae might adversely affect the native H. behrensii. Key Words:
Heteroptera, new records, adventive species, syntopy, stinging nettle, Urtica dioica DOI: 10.4289/0013-8797.115.2.xxx
Stinging nettle, Urtica dioica L. (Urticaceae), is a Holarctic perennial herb (Woodland 1982) characterized by a rich insect fauna in Britain (Davis 1973, 1983) and continental Europe (Davis 1989). Less attention has been given to documenting the insects of stinging nettle in North America. Among nettle-feeding Heteroptera are two lygaeoids of the family Heterogastridae: Heterogaster urticae (F.) in the Palaearctic (Servadei 1951, Southwood and Leston 1959, Pe´ricart 1998) and H. behrensii (Uhler) in the
Nearctic Region (Scudder 1985, 1996; Wheeler and Hoebeke 2010). We previously noted that H. urticae often is intercepted at U.S. ports of entry on plant material, machinery, and quarry products originating in western Europe, and provided morphological characters to distinguish this Eurasian and North African bug from the Nearctic H. behrensii. Based on fieldwork in the Pacific Northwest in 2008 and 2009, we gave additional Oregon records of H. behrensii and the first records for
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Washington State. Because we collected H. behrensii in Washington within 10 km of British Columbia, we suggested that it might be found on nettle in that province’s Lower Fraser Valley north of our Washington sites (Wheeler and Hoebeke 2010). Heterogaster behrensii was reported new to Canada from a site north of Oliver, British Columbia (Cannings 1981), but has not been recorded from additional Canadian locales (Scudder 1985, 1994; Maw et al. 2000). It is considered potentially rare and endangered in British Columbia (Scudder 1994, 1996). During fieldwork in British Columbia in 2010, we assumed that all specimens of Heterogaster collected from stinging nettle were those of H. behrensii. When material was examined with stereomicroscopy, we realized both H. behrensii and H. urticae were represented. In June 2011, we continued to sample stinging nettle in British Columbia. We give the first North American records of the Old World H. urticae, extend the known distribution of H. behrensii in British Columbia, and report the bugs’ syntopy in two colonies of U. dioica. We also provide morphological characters for distinguishing these superficially similar species. MATERIALS
AND
METHODS
Colonies of stinging nettle in British Columbia were sampled along roadsides and in other ruderal sites during late June–early July of 2010 and 2011; inflorescences and stems were swept or beaten into a shallow net. All adults of Heterogaster were collected and identified with stereomicroscopy. Voucher specimens have been deposited in the United States National Museum of Natural History, Smithsonian Institution, Washington, DC; Cornell University Insect Collection,
Ithaca, NY; and University of Georgia Collection of Arthropods, Athens, GA. Under specimens examined for both species, asterisks preceding locality names indicate sites of syntopy. All specimens were collected from U. dioica by the authors. Images of the habitus of each species were made with a Nikon D2 digital camera and 64 mm Zeiss Luminar lens with approximately 6-in (15.24 cm) bellows extension; 10 images were made of each bug species at different focal depths and combined to create a deep focus image, using Helicon Focus Pro software. Images of the fore legs of both species were made with an Olympus SZX12 dissecting microscope with a SPOT Insight 4 digital camera; multiple images were made at different focal depths and combined to create a deep focus image, again using Helicon Focus Pro software. RESULTS Heterogaster behrensii (Uhler) This heterogastrid is known only from western North America: British Columbia, Canada, south to Mexico (Baja California), and northeast to Idaho and Utah. Although bionomic data are scant, the bug appears to develop mainly on stinging nettle, U. dioica. Adults, including mating pairs, and nymphs of all instars have been found in July on stinging nettle in Oregon and Washington (Wheeler and Hoebeke 2010). Diagnosis.—Adults of the native H. behrensii (Figs. 1A, B) can be recognized by the following combination of characters: body oblong-oval, 6–7 mm long; generally dull brown and black; corium variable in color, mostly darker with some yellowish mottling, not strongly contrasting with the black scutellum; each hemelytron with a narrow, opaque,
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Fig. 1.
Heterogaster behrensii. A, Adult habitus; scale = 5 mm. B, Foreleg; scale = 1 mm.
black band at base of wing membrane adjacent to apex of corium (Fig. 1A, arrows); portion of clavus immediately adjacent to scutellum darkened throughout, remainder yellowish, except punctures black; dorsal surface of head, pronotum, scutellum, and corium covered with uniform vestiture of dense, silvery, appressed setae and some erect setae; three apical antennomeres darker dorsally, similar to color of scape; forefemora cylindrical, somewhat parallelsided, entirely black except for a small
pale spot dorsally at the apex; without sharp spine ventrally at apical 1/3; foretibiae as long as femora. British Columbia collections.—We collected H. behrensii five times. It was found in 2011 at three sites in the Lower Mainland’s Lower Fraser Valley, from Abbotsford east to near Bridal Falls. It occurred with H. urticae at a site on Vancouver Island in 2010 and one site in the Lower Fraser Valley in 2011. Mating pairs were observed at three of the five sites.
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Specimens examined.—CANADA: British Columbia, Lower Mainland, Abbotsford, Vye Rd., 49°00.9999N 122°17.0639W, 25 June 2011, 3♂, 5♀ (incl. a mating pair); *Abbotsford, jct. Rt. 11 & Clayburn Rd., 49°04.9209N 122°17.1839W, 26 June 2011, 5♂, 1♀; Bell Rd., 2 km E of Dewdney, 49°10.2969N 122°10.5589W, 26 June 2011, 1♂, 1♀ (mating pair); Rt. 9, N of Bridal Falls, 49°11.9499N 121°46.6789W, 26 June 2011, 2♂, 4♀(incl. a mating pair). Vancouver Island, *Duncan, 48°47.2269N 123°42.5899W, 28 June 2010, 1♂. Heterogaster urticae (F.) This Old World species, like its Nearctic congener H. behrensii, is known from species of Urtica, mainly U. dioca (Southwood and Scudder 1956, Southwood and Leston 1959, Davis 1973, Pe´ricart 1998). Nymphs and adults have been collected from plant families other than the Urticaceae (Whitehead 2007, Wheeler and Hoebeke 2010), but it is not known if non-urticaceous species support nymphal development. Widely distributed in the Palearctic Region (Pe´ricart 2001), H. urticae recently has become established in Norway, apparently due to the importation of plant material (Ødegaard and Endrestøl 2007, Sæthre et al. 2010). Its establishment in New Zealand and the Chatham Islands also might be the result of plant introduction (Scudder and Eyles 2003). In addition to its interception at U.S. ports of entry (Wheeler and Hoebeke 2010), H. urticae was intercepted in 2008 at a California border protection station (Yermo); an adult accompanied nursery stock shipped from Lake Las Vegas, Nevada (Garrison 2011). Heterogaster urticae has been collected from Uruguayan pampas grass (Cortaderia selloana (Schult. & Schult. f.) Asch. & Graebn.) in Riverside County,
California: San Jacinto, 10 November 2010, M. Lahti collector, 14♂, 6♀; Perris, 13 December 2010, M. Lahti, 7♂, 2♀ (specimens in California State Collection of Arthropods [CSCA], determined by Rosser Garrison). Diagnosis.—Adults of the immigrant H. urticae (Figs. 2A, B), like those of H. behrensii, are oblong-oval, 6–7 mm long, and dull brown to black. Heterogaster urticae, however, can be distinguished by the following combination of characters: corium mostly yellowish with distinct dark punctures and black patches, strongly contrasting with the black scutellum; opaque, black band lacking at base of wing membrane and apex of corium; clavus yellow, except punctures and apex black; dorsal surface of head, pronotum, scutellum, and corium with sparser vestiture of silvery appressed setae; three apical antennomeres mostly reddish yellow dorsally, contrasting with darker scape (some Internet images show all antennomeres infuscate); forefemora elongate, somewhat broadened, with a sharp spine (Fig. 2B, arrow) ventrally at apical 1/3 (sometimes smaller denticles also present distal to spine), mostly black, except apex distal to spine predominantly yellow on anterior and posterior surfaces; foretibiae slightly longer than femora. British Columbia collections.—Heterogaster urticae was taken alone four times: twice in the Metro Vancouver Area and twice on Vancouver Island. It was syntopic with H. behrensii at a site in the Lower Fraser Valley and another on Vancouver Island. Mating pairs were observed at four of the six sites. Specimens examined.—CANADA: British Columbia, Lower Mainland, Old Yale Rd. nr Scott Rd., Surrey, Whalley, 49°11.9249N 122°52.9029W, 26 June 2010, 14♂, 17 ♀ (incl. 5 mating pairs); Delta, Tsawwassen, 49°01.6349N 123°05.8849W,
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Fig. 2. Heterogaster urticae. A, Adult habitus; scale = 5 mm. B, Foreleg (note ventral spine at arrow); scale = 1 mm.
24 June 2011, 25♂, 17 ♀ (incl. 6 mating pairs); *Abbotsford, jct. Rt. 11 & Clayburn Rd., 49°04.9209N122°17.1839W, 26 June 2011, 1♂, 1♀. Vancouver Island, *Duncan, 48°47.2269N 123°42.5899W, 28 June 2010, 15♂, 14♀ (incl. 4 mating pairs); W of Westholme, 48°52.4809N 123°42.3499W, 30 June 2010, 4♂, 4♀ (incl. 3 mating pairs); Rt. 1A, 6 km S of Cedar, 49°03.1839N123°50.1289W, 1 July 2010, 1♀. DISCUSSION Our records of H. urticae from British Columbia’s Lower Mainland and Vancouver Island document its establishment in North America; previous
published records represent interceptions at ports of entry. The above label data from specimens taken in Riverside County, California, and other recent collections from southern California (Rosser Garrison, pers. comm.), suggest the bug’s establishment in the state. Seven other Palearctic lygaeoids have been reported from the Pacific Northwest since 1990 (Asquith and Lattin 1991, Henry and Adamski 1998, Wheeler and Stoops 1999, Lattin and Wetherill 2002, Henry 2004, Scudder et al. 2011). Heterogaster urticae probably is a recently established immigrant in the Pacific Northwest. That assumption gains support from the long-time presence in
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AU1
Vancouver of the lygaeoid systematist Geoffrey G. E. Scudder at the University of British Columbia (UBC). While an undergraduate (University of Wales) in his native Great Britain, he worked summers at the experimental station at Rothamsted and published on H. urticae (Southwood and Scudder 1956). Scudder also collected extensively in British Columbia during his tenure (1958–1999) at UBC (Cannings 2006, Scudder 2008). His interest in documenting the presence of adventive lygaeoids and other heteropterans in British Columbia and throughout Canada began with his arrival in Vancouver (Scudder 1958) and has continued (Scudder and Foottit 2006; Scudder 2007, 2013; Scudder et al. 2011). Familiar with the native H. behrensii (Scudder 1985), he recognized it as a species of special concern in the province (Scudder 1994). Scudder, therefore, was acquainted with both heterogastrid species and probably would have collected H. urticae in British Columbia (or been given specimens for identification) if detectable numbers had been present more than five or 10 years before our collections. We also extend the previously known Canadian distribution of H. behrensii— a single locale (near Oliver, BC) in the province’s South Okanagan—west to the Lower Fraser Valley and Vancouver Metro Area. The additional records might have led us to suggest that H. behrensii no longer merits inclusion among terrestrial insects considered potentially rare and endangered in British Columbia were it not for the recent establishment of the Palearctic H. urticae, which develops on the same host plant. The heterogastrids’ syntopy in two nettle colonies increases the likelihood of their further interaction. Some adventive species, after an initial period of low numbers, undergo explosive population growth (Crooks and
Soule´ 1999). At one site of syntopy in British Columbia, H. behrensii was collected in greater numbers (6 versus 2) than H. urticae, whereas more adults (29 versus 1) of H. urticae were found at a second site. The bugs’ co-occurrence on nettle is similar to that of two lygaeoid (artheneid) species on cattail (Typha spp.) in North America, except that they are not congeners and both are Palearctic immigrants. Chilacis typhae (Perrin) was detected first (Wheeler and Fetter 1987), followed by Holcocranum saturejae (Kolenati) (Hoffman and Slater 1995). In three mid-Atlantic cattail colonies that in the mid-1980s harbored only C. typhae, H. saturejae had become the dominant species when the same colonies were sampled in 1998 (Wheeler 2002). The further spread of H. urticae in British Columbia should be monitored. Adventive heteropterans previously reported from Canada apparently have not threatened native biodiversity (Scudder and Foottit 2006).Yet the immigrant H. urticae could pose a threat to the native H. behrensii. Behavioral and morphological studies of closely related species are facilitated by using populations that are syntopic rather than merely sympatric (Gannon 1998). In British Columbia, studies might determine if the two nettle-specialist heterogastrids minimize competition by partitioning host resources, as do two tropical milkweed (Asclepias)-feeding lygaeids of the genus Oncopeltus (Root and Chaplin 1976). ACKNOWLEDGMENTS We thank Rosser Garrison (Entomology Laboratory, California Department of Food & Agriculture, Sacramento) for access to the Heteroptera holdings in the CSCA, his help and hospitality when AGW visited in 2012, and communicating the current status of H. urticae in
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California; Kent Loeffler (Department of Plant Pathology, Cornell University) for the photographic images; Thomas Henry (Systematic Entomology Laboratory, USDA, ARS, Washington, DC) for verifying the identification of H. urticae; Robert Cannings (Royal British Columbia Museum, Victoria) for providing a copy of several articles on H. behrensii; and Peter Adler (School of Agricultural, Forest & Environmental Sciences, Clemson University) for suggestions that improved an early draft of the manuscript. This research was supported, in part, by the Cornell University Agricultural Experiment Station federal formula funds, Project No. NYC-139405 to ERH, received from Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture. Literature Cited Asquith, A. and J. D. Lattin. 1991. A review of the introduced Lygaeidae of the Pacific Northwest, including the newly discovered Plinthisus brevipennis (Latreille) (Heteroptera: Lygaeidae). Pan-Pacific Entomologist 67: 258–271. Cannings, R. 1981. New find in Okanagan nettles. Boreus 1(2): 9 (Newsletter of the Entomological Society of British Columbia). Cannings, R. A. 2006. Geoffrey G. E. Scudder: zoologist, conservationist, educator. Canadian Entomologist 138(4): ix–xxx. doi:10.4039/ n06-903 Crooks, J. A. and M. E. Soule´. 1999. Lag times in population explosions of invasive species: causes and implications, pp. 103–125. In I. Species and B. Management, eds. O. T. Sandlund, P. J. Schei, and A. Viken. Kluwer Academic Publishers, New York. 431 pp. Davis, B. N. K. 1973. The Hemiptera and Coleoptera of stinging nettle (Urtica dioica L.) in East Anglia. Journal of Applied Ecology 10: 213–237. doi:10.2307/2404726 Davis, B. N. K. 1983. Insects on nettles (Naturalists’ Handbooks 1). Cambridge University Press, Cambridge, UK. 64 pp. Davis, B. N. K. 1989. The European distribution of insects on stinging nettles, Urtica dioica L.: a field survey. Italian Journal of Entomology 56: 321–326.
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