Vespula acadica

(Sladen, 1918)

Forest Yellowjacket

Vespula acadica is a North in the Vespula rufa group, commonly known as the forest yellowjacket. It is distinguished by its preference for forested and nesting sites, typically building nests in decaying vegetation such as logs and leaf rather than in human structures. The exhibits relatively small colony sizes compared to other yellowjackets, with nests containing 75–400 . While generally avoiding human contact due to its habitat preferences, workers can be aggressive and persistent when colonies are disturbed, delivering repeated .

Vespula Acadica by Rick Avis. Used under a Attribution 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 acadica: /vɛˈspuːla əˈkeɪdɪkə/

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Identification

are black with markings and measure 10–15 mm in length. The underside of the is yellow rather than completely black, distinguishing it from some . Most reliably separated from the closely related Vespula atropilosa by the shape of the black marking on the second gastral : in V. acadica, the of the middle black region is rounded, whereas in V. atropilosa it is pointed.

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Habitat

Found primarily in forested environments including forests. Nests are built in decaying vegetation such as rotting logs, leaf , and other forest floor debris. Occasionally constructs aerial nests, though this is uncommon. Entrance tunnels are typically 15–25 cm long but may extend to 40 cm; the deepest subterranean nest recorded was 15 cm below the surface.

Distribution

North America. Range extends from Alaska down the West Coast to southern California and into the southwestern United States. In the eastern portion of its range, distribution is more northerly through the Great Lakes region and along the East Coast as far south as the Carolinas.

Seasonality

Colony cycle typically begins in mid-July with the onset of reproductive rearing. Most colonies complete their seasonal cycle by the last week of August or first week of September. colonies are founded by single in spring and die off in autumn after producing new queens and males.

Diet

Exclusively hunts live ; does not scavenge from carrion or human food sources. prey on live , , and . are obtained from natural sources. This restricted diet of live prey, rather than scavenging , reduces human encounters compared to other yellowjacket .

Life Cycle

colony cycle with haplometrotic (single ) nest founding. Colonies produce morphologically distinct queens and . Nests contain one worker-rearing and one to three reproductive-producing combs. Observed colonies are relatively small, with 75–400 workers and 3–4 combs total. The largest mature colony documented contained 425 workers, 70 males, and 78 queens, with four combs totaling 1,791 . New queens and males are produced in late summer for mating; queens overwinter to found new colonies the following spring.

Behavior

exhibit flexible and task fixation, with observed behaviors including inactivity, , nursing, , defense, and foraging. Mauling—agonistic interactions involving biting of the of the and —occurs among workers, particularly older individuals during colony decline. Males approach from the side to attempt mating, grasping the queen's thorax with all six legs; unreceptive queens curl their gaster toward their in a C-shape to prevent copulation. Workers do not thoroughly remove from below the , occasionally consuming liquid feces or feeding them to while leaving solids.

Ecological Role

of live including , , and , contributing to natural pest control in forest . Serves as for the obligate Vespula austriaca (in Europe) and Vespula infernalis (in North America), which usurp colonies and exploit forces. Nests may host (Sphecophaga , probably S. vesparum burra) and Fannia spp. on exterior surfaces.

Human Relevance

Limited direct interaction with humans due to forest preference. Not considered a significant pest because it does not scavenge from garbage or picnic areas. When colonies are disturbed, can be aggressive and persistent, delivering repeated . Stings are painful and may cause allergic reactions in sensitive individuals.

Similar Taxa

Vespula atropilosaVery similar black and coloration, but distinguished by the pointed (rather than rounded) of the middle black region on the second gastral .
Vespula consobrinaClose relative in the V. rufa group with similar colony biology and ; morphological separation requires detailed examination.