[1][2] It is native to regions of North America, largely in areas with northern temperate climates.

[6] The western yellowjacket shares the basic yellow and black pattern with other species of social wasps in the genus Vespula.

Though both species have a similar diamond-shaped black mark on the first tergum, V. pensylvanica can usually be differentiated by the continuous yellow ring (often referred to as an eye-loop) present around each eye.

In such cases, V. pensylvanica can be identified by a spotted mark on the frons below the antenna, a slender aedeagus, and a denser apical region of tergum 7.

[7] Western yellowjackets build large nests made of wood fibers, enclosed in a hexagonal paper envelope with a small 10– to 30-cm entrance tunnel at the bottom.

pensylvanica can be found in open forest, prairies, urban zones, gardens, parkland, meadows, and houses.

Within four days of emergence, workers begin foraging for fiber, nectar, water, and prey, larval feeding, construction of envelope and cells, nest sanitation, guarding and colony defense, thermal regulation; and “mauling” or aggressive behavior.

Sometimes, yellowjackets enter and leave in a slow but steady traffic faced by opposition from honey bee workers.

[15] V. pensylvanica utilize their mandibles to scrape weathered wood and dried herbaceous stems to obtain resources rich in fiber.

To feed developing larvae, the queen captures prey by incapacitation, trims it to an appropriate size for carrying, and brings it back to the nest to further malaxate the item.

[13] Workers forage for food, capture and malaxate prey, defend territories, and monitor the distribution of resources among larvae.

In addition, a pre-defecation head dance occurs in both workers and the queen, and this fecal material is then removed.

As a result, kin selection posits that workers will be more inclined to show altruistic behavior toward sisters than brothers.

[19] Though colonies of V. pensylvanica are generally monogynous and annual, polygyny and overwintering has been observed in non-native regions, specifically in Hawaii.

First, daughter queens remaining in the natal nest possibly create kin associations that provide a mechanism allowing the benefits of polygyny to outweigh the costs.

In both cases, genetic relatedness and kin selection could explain why polygyny has emerged in non-native regions.

[4] V. pensylvanica also preys on D. silvestris and other Drosophila flies native to Hawaii, disrupting the local ecosystem.

[22] The ability to kill prey relies on three major characteristics of the targeted insects: their presence within foraging range, their acceptability, and the ease by which they can be captured.

During cool temperatures, Hylaeus species spend time in the sun making them vulnerable to attack by yellowjackets.

In a study on yellowjacket predation at Hawaii volcanoes and Haleakala National Parks in 1992, many of the Lepidoptera were taken as larvae.

The females of T. lugubris are typically the first arthropods to locate and exploit V. pensylvanica colonies under conditions favorable for nest associates.

Concentrated garbage has become an alternative food supply, and colonies have emerged in and around areas of human impact, such as recreational parks and resorts.

Because the chance of colony disturbance and resulting stings is great, the species is recommended to be controlled during outbreaks.

Those who are highly sensitive or allergic to stings should speak to a physician about alternatives such as emergency kits with premeasured doses of epinephrine or desensitization procedures.

The tendency of V. pensylvanica to cluster in areas of human impact has created problems for pickers in fruit orchards who are frequently stung.

The period of outbreaks previously described can be financially burdensome for people engaging in logging, raising fruit, or in recreation-associated activities.

[2] Two major strategies used for monitoring and controlling V. pensylvanica include trapping with synthetic chemical attractants and tree shaking.

[24] Using a vial dispenser, releasing up to an estimated 2.3 mg of heptyl butyrate per hour increased the number of yellowjackets attracted.

Although V. pensylvanica typically resides in ground nests, queens occasionally choose these trees as overwintering sites.

One potential strategy to reduce the number of yellowjackets and other generalist predators is applying preharvest permethrin sprays in combination with mechanical tree-shaking.