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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

 

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65. Symmorphus canadensis (de Saussure, 1855)
Figs B2.7; B8.2, 4, 6, 10; C65.1–5.

Symmorphus canadensis Symmorphus canadensis Symmorphus canadensis
Symmorphus canadensis Symmorphus canadensis Symmorphus canadensis Symmorphus canadensis

Species recognition. This species is easily confused with S. cristatus. Some diagnostic characters used by previous authors proved to be unreliable. The width/length ratio of tergum 1, which is one of the main diagnostic characters in Cumming’s (1989) key, shows significant allometric variation. Small specimens of S. cristatus have a more slender tergum 1 (medial postcarinal length up to 0.78x apical width) than larger specimens (medial postcarinal length 0.61–0.69x apical width; Cumming 1989), and cannot be separated from S. canadensis (medial postcarinal length 0.71–0.81x apical width; Cumming 1989) based on this character. However, both males and females of the two species can be reliably distinguished based on the newly discovered character of the pubescence of the ventral surface of the hind femur and other characters mentioned in the key.

Variation. Fore wing length 5.0–6.8 mm (♂♂), 4.5–7.3 mm (♀♀). Body with pale markings usually deep yellow, ivory only in northern specimens. Female clypeus with pale basal spot narrow to wide, often absent. Interantennal spot rarely absent in male. Anteroventral surface of scape usually black in female, sometimes with more or less extensive pale basal mark. Pronotum with a pair of pale spots of variable size, very small in some males. Pair of pale spots on scutellum sometimes absent in male. Tegula black or brownish, sometimes marked with pale. Apical fasciae typically developed on terga 1, 2 and 4 (exceptionally missing on 4), almost always absent on 3 and 5 in female, more often present in male. Sternum 2 with posterolateral pale spots or an interrupted fascia; occasionally sternum 4 and more rarely 3 with posterolateral spots, especially in male.

Distribution. Distributed throughout Canada and the U.S., except arctic, high boreal and southwestern desert regions; not recorded from NF, LB, YT, NU and AK (Cumming 1989).

Biology. Nests in borings in wood and twigs, and uses mud for cell partitions and closing plugs. Preys on leaf-mining Coleoptera and Lepidoptera larvae, predominantly Chrysomelidae (especially Chalepus spp.), more rarely on Gracillariidae, Cosmopterigidae and Curculionidae (Apion, Prionomerus) (Krombein 1967, 1979).

 

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