WESTERN YELLOW JACKET Vespula pennsylvanica

Although there are seventeen species of yellow jackets in North America, the one that people are most likely to have an encounter with in urban areas is the Western Yellow Jacket. Yellow jackets are beneficial because they are pollinators and they feed on a lot of soft-bodied insects such as caterpillars and flies that are often harmful.

Adult wasps are ½ to 3/4 inch long, with characteristic yellow and black stripes and transparent wings. Yellow jackets are often feared for their sting, which is a hazard to people who are allergic. However, they are beneficial as predators of caterpillars, flies and beetle grubs. Nests need not be removed if they are not interfering with the lives of people in the area.

Identification: Most people know what the yellow jackets look like, the classic wasp with black and yellow markings on the head, thorax and abdomen. The various species are very similar, however, and identification should be left to the experts.

Distribution: The Western Yellow Jacket is found throughout Canada and the United States primarily west of the 100th meridian and south into Mexico. Western Yellow Jackets have now colonized many cities in eastern North America. In the southern part of its range it is found largely at higher elevations. Various species of yellow jackets are found virtually everywhere in North America.

Habitat and habits: In most of North America, yellow jacket colonies are seasonal, dying off in the winter. Yellow jackets build their nests either in the ground or attached to branches of bushes or trees, and sometimes buildings, depending on the species. The Western Yellow Jacket is a ground nester and often builds a nest under peoples' porches or steps and in appropriate cracks in sidewalks and buildings. It is also a scavenger as well as being a hunter where most other species are exclusively predators, and for this reason it is often a pest when people eat outside. It is this scavenging habit that allows it to remain active so late in the fall. In cold climates yellow jacket colonies die out completely in the winter, except for the new queens. An overwintering queen will establish a new colony in the spring, never using the old nest. In subtropical areas some species may form perennial colonies resulting in much larger nests.

Life Style: Yellowjackets are social wasps living in colonies containing workers, queens and males. Colonies are annual with only inseminated queens overwintering. Fertilized queens occur in protected places as hollow logs, in stumps, under bark, in leaf litter, in soil cavities and human-made structures. Queens emerge during the warm days of late February to early April, select a nest site and build a small paper nest in which eggs are laid. After eggs hatch from the 30 to 50 brood cells, the queen feeds the young larvae for about 18 to 20 days. Larvae pupate, emerging later as small, infertile females called workers..

Closely related species: As stated earlier, separating the various species by appearance is best left to the experts. The one exception to this is the Bald-faced Hornet (Dolichovespula maculata). These aerial nesters are larger than the yellow jackets and have white markings rather than yellow. But even here the issue is confused because there are two other black
and white species, the Black Jacket (V. consobrina) and D. arctica which has no common name. Both of these, however, have white markings on the first three abdominal segments, which are lacking on the Bald-faced Hornet.

Comments: Nobody likes to be stung by yellow jackets, and some fear of them is quite common. Unfortunately, this fear can become irrationally strong, especially in people who have never been stung or only been stung when they were quite young. Irrational fear can translate into irrational behavior that is more likely to result in being stung or the person hurting themselves in some way. Panicking and flailing one's arms around is not the thing to do. Here are some hints to avoid being stung when yellow jackets are numerous and persistent. Don't panic. Avoid eating or drinking sweet drinks outside, especially in the fall when the yellow jackets are most aggressive, and near a known colony. Don't wear perfumes, colognes etc., because yellow jackets are attracted to anything that smells like flowers. For the same reason don't wear brightly colored clothing, especially with floral patterns. If you must have a picnic outside when yellow jackets are bad, try putting out a commercial trap some time before hand to reduce the numbers. Remember that yellow jackets are beneficial because they are pollinators and they feed on a lot of soft-bodied insects such as caterpillars and flies that are often harmful.