Yellowjackets have sometimes been mistakenly called "bees", but they are actually in the "wasp" family. A typical yellowjacket worker is about 12 mm (0.5 in) long, with alternating bands on the abdomen while 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. Yellowjackets, in contrast to honey bees, are not covered with tan-brown dense hair on their bodies and lack the flattened hairy hind legs used to carry pollen. 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/wasp venoms, is primarily only dangerous to those who are allergic, unless a victim receives a large number of stings (main article: Bee sting). All species have yellow or white on the face. Mouthparts are well-developed with strong jaws called mandibles for capturing and chewing insects, with a proboscis for sucking nectar, fruit, and other juices. Nests are built 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. Nests are made from wood fiber chewed into a paper-like pulp.
Due to their aggressive behavior, including stinging, many other insects exhibit mimicry of yellowjackets; in addition to numerous bees and wasps (Müllerian mimicry), the list includes some flies, moths, and beetles (Batesian mimicry).
Yellowjackets' 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.
