YellowJackets

Yellow jacket is the common name in North America for predatory wasps of the genera Vespula and Dolichovespula. Members of these genera are known simply as “wasps” in other English-speaking countries. Most of these are black and yellow; some are black and white (such as the bald-faced hornet, Dolichovespula maculata), while others may have the abdomen background color red instead of black. They can be identified by their distinctive markings, small size (similar to a honey bee), their occurrence only in colonies, and a characteristic, rapid, side to side flight pattern prior to landing. All females are capable of stinging. Yellow jackets are important predators of pest insects.

Yellow jackets are often called “bees” as they are similar in size and appearance, and both sting, but are actually wasps. A typical yellow jacket worker is about 12 mm (0.5 in) long, with alternating bands on the abdomen; the queen is larger, about 19 mm (0.75 in) long (the different patterns on the abdomen help separate various species). Workers are sometimes confused with honey bees, especially when flying in and out of their nests. Yellow jackets, in contrast to honey bees, are not covered with tan-brown dense hair on their bodies, They do not carry pollen and do not have the flattened hairy hind legs used to carry it. They have a lance-like stinger with small barbs and typically sting repeatedly, though occasionally the stinger becomes lodged and pulls free of the wasp’s body; the venom, like most bee and wasp venom, is primarily only dangerous to humans if allergic, unless a victim is stung many times (main article: Bee sting).

All species have yellow or white on the face. Mouth-parts are well-developed with strong mandibles for capturing and chewing insects, with a proboscis for sucking nectar, fruit, and other juices. Yellow jackets build nests in trees, shrubs, or in protected places such as inside human-made structures (attics, hollow walls or flooring, in sheds, under porches, and eaves of houses), or in soil cavities, mouse burrows, etc. They build them from wood fiber they chew into a paper-like pulp. Many other insects exhibit protective mimicry of aggressive, stinging yellow jackets; in addition to numerous bees and wasps (Müllerian mimicry), the list includes some flies, moths, and beetles (Batesian mimicry).
Yellow jackets’ closest relatives, the hornets, closely resemble them but have a much bigger head, seen especially in the large distance from the eyes to the back of the head. Yellow jackets are social hunters living in colonies containing workers, queens, and males. Colonies are annual with only inseminated queens overwintering. Fertilized queens occur in protected places such 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 spring or early summer, select a nest site, and build a small paper nest in which they lay eggs. After eggs hatch from the 30 to 50 brood cells, the queen feeds the young larvae for about 18 to 20 days. After that, the workers in the colony will take over caring for the larvae, feeding them with chewed up food, meat or fruit (called trophallaxis). Larvae pupate emerge later as small, infertile females called workers. By mid-summer, the first adult workers emerge and assume the tasks of nest expansion, foraging for food, care of the queen and larvae, and colony defense. From this time until her death in the autumn, the queen remains inside the nest, laying eggs. The colony then expands rapidly, reaching a maximum size of 4,000 to 5,000 workers and a nest of 10,000 to 15,000 cells in late summer. At peak size, reproductive cells are built with new males and queens produced. Adult reproducers remain in the nest fed by the workers. New queens build up fat reserves to overwinter. Adult reproducers leave the parent colony to mate. After mating, males quickly die, while fertilized queens seek protected places to overwinter. Parent colony workers dwindle, usually leaving the nest to die, as does the queen. Abandoned nests rapidly decompose and disintegrate during the winter. They can persist as long as they are kept dry, but are rarely used again. In the spring, the cycle is repeated; weather in the spring is the most important factor in colony establishment.

Adults feed primarily on items rich in sugars and carbohydrates such as fruits, flower nectar, and tree sap, and larvae feed on proteins such as insects, meats, and fish. Adult workers chew and condition the meat fed to the larvae. Larvae in return secrete a sugar material relished by the adults; this exchange is a form of trophallaxis. In late summer foraging workers change their food preference from meats to ripe, decaying fruits, or scavenge human garbage, sodas, picnics—where they are a common and unwelcome nuisance—etc., since larvae in the nest fail to meet requirements as a source of sugar. Yellow jacket nests usually last for only one season, dying off in winter. The nest is started by a single queen, called the “foundress”. Typically, a nest can reach the size of a basketball by the end of a season.
In parts of Australia, New Zealand, the Pacific Islands, and southwestern coastal areas of the United States, the winters are mild enough to allow nest overwintering. Nests that survive multiple seasons become massive and often possess multiple egg-laying queens.