Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region
Matthias Buck, Stephen A. Marshall, and David K.B. Cheung
Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Taxonomy. This species has usually been referred to as V. intermedia (du Buysson, 1905) in the North American literature (e.g., Miller 1961, Akre et al. 1981, Carpenter 1987). It differs from typical V. rufa (from Europe and western Asia) in possessing ivory instead of yellow markings. Eastern Palaearctic populations are also marked with ivory but in most areas they show more reduced ferruginous suffusions of terga 1 and 2 (Archer 1981). This form has been called V. rufa schrenckii (Radoszkowski, 1861). Due to the variability of ferruginous markings, which can be observed in both Palaearctic and Nearctic specimens, Archer (1997) synonymized intermedia with rufa schrenckii. However, pale-marked populations also occur within the range of the nominate subspecies (i.e., in Sweden, Turkmenistan, southern Kazakhstan; see Archer 1997. Note that Archer considered the ‘subspecies’ of V. rufa more as colour forms rather than formal taxa.).
Species recognition. This rarely collected subarctic species can immediately be separated from other Vespula species by the presence of ferruginous markings on terga 1 and 2. Pale markings are ivory as in V. consobrina. Workers and males of the largely sympatric Dolichovespula norwegica show a similar colouration but they lack enclosed ivory spots near the summit of tergum 1 and sometimes also lack ferruginous markings on the same tergum.
Variation. Fore wing length 10.0–11.0 mm (workers), 12.5–13.0 mm (♀♀, n = 5), 11.0–12.0 mm (♂♂, n = 5). Black clypeal spot usually extending to both dorsal and ventral margins of clypeus, sometimes only narrowly so, occasionally not attaining ventral margin. Lower gena of female black, sometimes with small ivory spot; male with complete, medially narrowed or interrupted pale band, but sometimes lower gena black except for a small pale spot. Metanotum with or without pair of ivory spots; the spots usually small. Ferruginous markings of metasoma on average more extensive in worker than in queen or male. Tergum 1 of worker largely ferruginous with ivory markings, black area usually restricted to relatively small spot on anterior, vertical surface, occasionally also with small median spot between pair of basal ivory spots. Tergum 1 of queen sometimes largely black on anterior surface and with large median and small lateral black spots on posterior, horizontal surface. Tergum 2 with large, ferruginous, lateral spots, sometimes confluent posteriorly in worker; often very reduced to nearly absent in queen. Sternum 2 largely ferruginous, sterna 3 and 4 sometimes with ferruginous spots as well. Posterior margin of black basal area of terga nearly straight in worker, with slightly prominent, paired, lateral convexities in queen; terga never with free black discal spots.
Distribution. Canada: transcontinental in the north with records from all provinces and territories except NU. Northern U.S.: AK, VT and NY. Palaearctic (and adjacent Oriental): from western, northern and central Europe to Kamchatka, Japan, China, Taiwan, south to Turkey, Uzbekistan and Nepal (Carpenter and Kojima 1997).
Biology. The biology of Nearctic populations has not been studied (Akre et al. 1981). In the Palaearctic the species nests usually below ground (often very close to the surface), more rarely in cavities above ground (hollow stumps. wall cavities, bird boxes), under moss, in dense bushes, under eaves of houses or in attics (Archer 1997). Like other species in this group V. rufa preys on live arthropods only and does not scavenge on carrion.