Key to eastern Nearctic Symmorphus species

Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region
CJAI 05, February 19, 2008
doi: 10.3752/cjai.2008.05

Matthias Buck, Stephen A. Marshall, and David K.B. Cheung

Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1

Symmorphus Wesmael

The genus Symmorphus is mainly Holarctic and Oriental but reaches northern parts of the Neotropical region. Four species occur in North America, one of which is restricted to British Columbia and the western United States (Cumming 1989).

Reference. – Cumming, 1989 (World revision, key).

8. Key to eastern Nearctic Symmorphus species

1.	Metasomal tergum 1 broad (Fig. 8.8), median postcarinal length 0.44–0.55x apical width of tergum. Male: flagellomere XI large, at least as long as broad (Fig. 8.1). Female: flagellomere I longer than maximum width of flagellum; cephalic foveae small, separated by at least four times their own width (Fig. 8.3); hair below base of fore femur long, some hairs at least one mid ocellar diameter long	*S. albomarginatus* (de Saussure)
-	Metasomal tergum 1 more elongate, median postcarinal length 0.61–0.83x apical width of tergum (Figs 8.9–10). Male: flagellomere XI smaller, length 0.55–0.94x width (as in Fig. 8.2 or smaller [after Cumming 1989]). Female: flagellomere I shorter than maximum width of flagellum; cephalic foveae separated by at most three times their own width (Figs 8.4–5); hair below base of fore femur shorter (length less than 0.5x mid ocellar diameter but sometimes with a few longer hairs)	2
2.	Hair below basal half of hind femur extremely short (length ca. 0.2x mid ocellar diameter), of nearly uniform length and very dense, the brush thus of regular appearance (almost velvet-like) (Fig. 8.6). Cephalic foveae of female very large, separated by at most 1.5x their own diameter (Fig. 8.4)	*S. canadensis* (de Saussure)
-	Hair below basal half of hind femur longer (length ca. 0.3x mid ocellar diameter), less dense, usually with some longer hairs admixed between shorter hairs, the brush thus appearing irregular, length of hairs noticeably decreasing distally (Fig. 8.7). Cephalic foveae of female smaller, separated by at least 2.5x their own diameter (Fig. 8.5 )	*S. cristatus* (de Saussure)

Metasoma of Symmorphus species