Akre, R.D., A. Greene, J.F. MacDonald, P.J. Landholt, and H.G. Davis. (1981). Yellowjackets
of North America, North of Mexico. U.S. Department of Agriculture, Washington, D.C. Handbook
Vespula atropilosa (prairie yellowjacket) is found in western North America where it is restricted to the Canadian and Transition Zones of the Boreal Region (fig. 44). Detailed biological and behavioral investigations reported by Akre et al. (1976) and MacDonald 51. (1974. 1975a. 1975b).
V. atropilosa is abundant in prairie and open t areas, but becomes increasingly less abundant in heavy forest where it is replaced by V. acadica. It also commonly nests in yards, pastures, golf courses, and similar areas.
V. atropilosa was reported as a subterranean by Bequaert (1931), Bohart and Bechtel (1957), Buckell and Spencer (1950), and Miller (1961). MacDonald et al. (1974, 1975a) reported locations of 40 nests of V. atropilosa near Pullman, Wash. Thirty-six were subterranean, and the remaining four were in various locations
—under sod pile, inside decayed 4- by 4-inch timber (fig. 45f), in tree hollows, and beneath steps. From 1974 to 1977, an additional 55 colonies were located; 3 were nesting in between walls of houses, and the other nests were subterranean. Most nests were built in rodent burrows with the nest located 10 to 30 cm into the tunnel and 10 to 15 cm below the soil surface.
In the spring of 1977, an old (1976) nest of V. atropilosa, containing 730 cells in 2 combs, was found in a truly aerial position in Pullman. The nest was 150 cm above the ground—located underneath a concrete overhang, which was part of some steps—and was fastened to concrete on two sides and to plywood on the top.
Table 5 compares mature (with reproductive cells) V. atropilosa colonies from 1971 to 1975. All colonies collected during 1976-77 were excluded as they were used in experiments. Nest size varied from year to year with the nest of the smallest mature colony comprised of 278 cells; the largest, 2,676. When collected, the greatest number of workers in a colony was 504. This is typical of colonies and nests of all members of the V. rufa group, which are only one-fifth to one-fourth as large as those of members of the V. vulgaris group (table 1).
V. atropilosa workers are predators only on live prey. They often attack spiders, phalangids, flies, caterpillars, hemipterans, and some homopterans, but seldom attack other Hymenoptera or beetles.
Nest associates of V. atropilosa were studied by MacDonald et al. (1975b). Most associates are scavengers in debris below the nest or on fungi growing on the nest carton. Nests of V. atropilosa are quite filthy, with remnants of bodies and other debris incorporated into the nest envelope and carton, probably providing scavengers still another supply of food. The pupal parasite, Sphecophaga vesparum burra, appears to adversely affect development of young colonies. This is an abundant species and some colonies invariably nest in yards, causing homeowners concern and often warranting removal; however, workers are usually no problem unless the colony is disturbed.
Reprinted with permission from: Miller, C.D.F. 1961 Taxonomy and Distribution of Nearctic Vespula. The Canadian Entomologist Supplement 22.
Color.—Black with yellow markings.
Structure.—Malar space less than half as long as the penultimate antennal segment (Fig. 1); occipital carina incomplete (Fig. 4); abdominal tergites extensively covered with long erect hairs; digitus of male genitalia nearly half as long is distal, saddle-shaped portion of aedeagus (Fig. 15).
Abdominal Color Patterns.—as in Figs. 32, 35, 38.
Facial Color Pattern.—as in Fig. 72.
This Nearctic species is restricted to the Canadian and Transition zones of the Boreal region in western North America. Specimens have been taken as far north at Fort McLeod, British Columbia, and Medicine Lake, Alberta.
Miller (1958) demonstrated why this entity deserves specific recognition.
Like V. acadica it is readily distinguished over its entire range. The rare occurrence of male specimens, which have intergradient color patterns between it and V. acadica, is unexplainable with the evidence available. It might be assumed that they are the result of hybridization between the two species or overlapping intraspecific variation (parallel evolution). The author continues to recognize V. atropilosa as a good species.
Ecological Notes.—The nest of this species is reported by Bohart (1957) as being terrestrial.