Vespula atropilosa

(Sladen, 1918)

Prairie Yellowjacket

Vespula atropilosa, the prairie yellowjacket, is a social native to western North America. It forms underground colonies in prairie and grassland , typically nesting in abandoned rodent burrows. Unlike scavenging yellowjackets, it is strictly predatory, hunting live insects to feed its larvae. The exhibits male color with xanthic (yellow) and melanic (black) abdominal variants.

Vespula atropilosa by (c) Peter Abrahamsen, some rights reserved (CC BY), uploaded by Peter Abrahamsen. Used under a CC-BY license.

Vespula atropilosa by (c) Alaina Krakowiak, some rights reserved (CC BY), uploaded by Alaina Krakowiak. Used under a CC-BY license.

Vespula of North America faces by Lynn S. Kimsey and James M. Carpenter. Used under a CC BY 3.0 license.

Pronunciation

How to pronounce Vespula atropilosa: /vɛsˈpuːla ˌætrəˈpaɪloʊsə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from Vespula pensylvanica (western yellowjacket) by strictly predatory —V. atropilosa does not scavenge carrion or human food. Separated from Vespula rufa by morphological characters including the incomplete occipital carina and specific proportions of the malar space. Male color dimorphism (xanthic and melanic phases) is characteristic but not unique. Nest architecture differs from aerial-nesting Dolichovespula by being subterranean.

Images

Habitat

Prairie and grassland . Nests in large open areas including pastures, golf courses, dry fields, and rural yards. Nests are subterranean, typically established in preexisting rodent burrows on flat or sloped terrain at depths of 3–23 cm below the soil surface. Nests on slopes tend to be deeper. Queens select remote edges of burrows for nest establishment.

Distribution

Western North America. In the United States: Washington, Oregon, California, Idaho, western Montana, Wyoming, Utah, most of Colorado, northern New Mexico, Arizona, and eastward to Wisconsin and Illinois. In Canada: British Columbia, Alberta. Range extends from central British Columbia south and east through the Western and Midwestern United States.

Seasonality

Queens emerge from hibernation in late April to early May. Colony establishment occurs in spring. numbers peak in mid-summer with maximum worker construction in early July. cell construction peaks in late July. males emerge from late July through mid-August. New queens emerge from early August through mid-September, with peak in mid-August to early September. Colonies decline by September-October.

Diet

Strictly predatory. capture live insects including Diptera (flies), Hemiptera (particularly such as aphids, cicadas, and leafhoppers), Lepidoptera ( and butterflies, especially larvae), grasshoppers, lacewings, and spiders. Preferred prey includes Hemiptera, lacewings, and spiders. Adults consume nectar and honeydew for energy.

Life Cycle

colony cycle. Queens overwinter in hibernation, typically under bark on stumps and logs. In spring, queens establish nests alone, rearing 4–9 initial . Workers assume foraging duties once emerged. Colony grows through summer with nest sizes averaging 1,200 (range 550–2,200). Mature nests contain 2–3 cell combs with 200–900 queen cells. New queens and males produced in late summer mate before queens enter hibernation. Colony dies in fall; only new queens survive winter.

Behavior

Strictly predatory foraging — hunt live prey and do not scavenge. Workers malaxate (chew) prey after capture and fly off quickly to avoid theft by nestmates. Prey theft between workers has been observed in confined conditions but not in natural . Mating occurs mid-day with males pursuing queens in ; multiple males compete, frequently interrupting copulations which average one minute in duration. Queens mate with multiple males. Males grasp queens tightly by the during mating. Workers exhibit kin typical of haplodiploid social insects.

Ecological Role

of agricultural and garden pest insects including caterpillars, aphids, flies, and grasshoppers. Contributes to natural of herbivorous insects. may visit flowers for nectar, potentially providing minor pollination services. Serves as prey for various vertebrate and predators. Nests are exploited by including beetles (Cryptophagus pilosus) and flies (Fannia spp., Dendrophaonia querceti) late in the colony cycle.

Human Relevance

Generally not considered a pest due to non-scavenging . rarely pose threat unless colony is disturbed. May nest in rural yards in the Pacific Northwest. Provides beneficial pest control services by preying on lacebugs and caterpillars. Attracted to heptyl butyrate and meat baits used in traps, though trapping effectiveness for reduction is questionable. Venom used in sting therapy extracts. Stings can occur if nests are disturbed.

Similar Taxa

Vespula pensylvanicaOverlapping distribution and similar appearance, but V. pensylvanica is both and scavenger, frequently pestiferous at human food sources. V. pensylvanica queens remain stationary during mating and mate for longer durations (2–11 minutes versus ~1 minute). V. pensylvanica has dark .
Vespula rufaFormerly considered or ; distinguished by morphological characters including malar space proportions and occipital carina structure.
Dolichovespula maculataSimilar black and white or black and yellow patterning, but builds aerial nests rather than subterranean nests, and is generally less aggressive.

More Details

Taxonomic History

Formerly classified as Vespa atropilosa. Bequaert (1931) treated it as a xanthic form of Vespula rufa; Bohart and Bechtel (1957) considered it a of V. rufa; Miller (1961) recognized it as a distinct .

Nest Architecture

Nests constructed from envelope paper made of weathered wood and non-woody plant fibers, resulting in multi-colored horizontal strips. Nests are relatively 'dirty' compared to other , incorporating bodies of deceased and debris into the paper envelope. Nests typically have a single entrance tunnel and contain a single comb above .

Venom Characteristics

Possesses relatively small compared to Vespula infernalis. Queens carry more venom than ; an average worker can kill at least 15 other workers with its venom supply, while killing a requires approximately one-third of a worker's total venom.