Vespula pensylvanica

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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94. Vespula pensylvanica (de Saussure, 1857) – Western Yellowjacket
Figs B13.12, 23, 25, 26, 47, 64, 75; C94.1–10.

Species recognition. The metasomal pattern of V. pensylvanica is very similar to V. germanica, but it is the only species in the V. vulgaris-group that possesses a yellow eye-loop. Occasionally, in males the eye loop is completely absent (it can be more or less broadly interrupted in both sexes but rarely so in females). Males without a yellow eye loop can be distinguished from V. germanica by the deeply emarginate or spotted subantennal mark on the frons, the slender preapical portion of the aedeagus, and the much more densely pubescent apical margin of tergum 7 (see key). A narrow eye loop is also present in most females of V. squamosa (squamosa species group) but this species shows a radically different metasomal pattern.

Variation. Fore wing length 8.5–10.5 mm (workers), 12.5–14.5 mm (♀♀; Jacobson et al. 1978), 12.5–14.0 mm (♂♂). Variation otherwise not studied.

Distribution. Canada: MB to BC, firstly recorded as an adventitious species for ON. Western U.S. east to WI, NE, CO and TX. Mexico: Baja California Norte, México and Michoacán. Introduced to Hawaii (Carpenter and Kojima 1997). According to Akre et al. (1981) occurrence east of the 105th meridian is scattered. The single Ontario record is the easternmost known for V. pensylvanica, but the species has apparently not become established in the province.

Biology. Nest are usually subterranean but are also built in other dark cavities like hollow walls and attics. Females prey on a wide variety of arthropods (occasionally even on slugs) besides scavenging on carrion. This is the most significant pest yellowjacket in western North America (Akre et al. 1981).

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