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 like the bald-faced hornet, Dolichovespula maculata. Others may have the abdomen background color red instead of black. They can be identified by their distinctive markings, their occurrence only in colonies, and a characteristic, rapid, side to side flight pattern prior to landing. All females are capable of stinging. Despite having drawn the loathing of humans, yellow jackets are in fact important predators of pest insects.
Yellow jackets are sometimes mistakenly called "bees", as they are similar in size and appearance and both sting, but they are actually wasps. Yellow jackets may be confused with other wasps, such as hornets and paper wasps. Polistes dominula, a species of paper wasp, is very frequently misidentified as a yellow jacket. 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 their abdomens 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.
These species have lance-like stingers with small barbs, and typically sting repeatedly, though occasionally a stinger becomes lodged and pulls free of the wasp's body; the venom, like most bee and wasp venoms, is primarily only dangerous to humans if allergic, unless a victim is stung many times. All species have yellow or white on their faces. The mouthparts are well-developed with strong mandibles for capturing and chewing insects, with probosces for sucking nectar, fruit, and other juices. Yellow jackets build nests in trees, shrubs, or in protected places such as inside man-made structures, 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).
Life cycle and habits 
Yellow jackets are social hunters living in colonies containing workers, queens, and males. Colonies are annual with only inseminated queens overwintering. Fertilized queens are found in protected places such as hollow logs, in stumps, under bark, in leaf litter, in soil cavities, and man-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. Larvae pupate, then emerge later as small, infertile females called workers. By midsummer, 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 reproductives remain in the nest fed by the workers. New queens build up fat reserves to overwinter. Adult reproductives 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 foundress 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, etc., since larvae in the nest fail to meet requirements as a source of sugar.
Notable species 
- European yellow jackets (the German wasp, Vespula germanica and the common wasp, Vespula vulgaris) were originally native to Europe, but are now established in North America, southern Africa, New Zealand, and eastern Australia
- The Eastern yellowjacket (Vespula maculifrons), and western yellow jacket (Vespula pensylvanica), are native to North America
- The Southern yellowjacket, Vespula squamosa
- Bald-faced hornets, Dolichovespula maculata, belong among the yellow jackets rather than the true hornets, but are not usually called "yellow jackets" because of their ivory-on-black coloration.
- Tree wasp, Dolichovespula sylvestris
Dolichovespula species such as the aerial yellow jacket, Dolichovespula arenaria, and the bald-faced hornet, tend to create exposed aerial nests. This is a feature shared with some true hornets, which has led to some naming confusion.
Vespula species, in contrast, build concealed nests, usually underground.
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.
In the United States 
In 1975, the German yellowjacket (Vespula germanica) first appeared in Ohio, and has now become the dominant species over the Eastern yellowjacket. It is bold and aggressive, and if provoked, it can sting repeatedly and painfully. It will mark aggressors, and will pursue them if provoked. The German yellow jacket builds its nests in cavities — not necessarily underground — with the peak worker population in temperate areas between 1,000 and 3,000 individuals between May to August, each colony producing several thousand new reproductives after this point, through November. The eastern yellow jacket builds its nests underground, also with the peak worker population between 1,000 and 3,000 individuals similar to the German yellow jacket. Nests are built entirely of wood fiber and are completely enclosed except for a small entrance at the bottom. The color of the paper is highly dependent on the source of the wood fibers used. The nests contain multiple, horizontal tiers of combs within. Larvae hang down in combs.
In the southeastern United States, where southern yellow jacket (Vespula squamosa) nests may persist through the winter, colony sizes of this species may reach 100,000 adult wasps. The same kind of nest expansion has occurred in Hawaii with the invasive western yellow jacket, Vespula pensylvanica.
In popular culture 
The yellow jacket's most visible place in American popular culture is as a mascot, most famously with the Georgia Tech Yellow Jackets, represented by the mascot Buzz. Other college and university examples include the American International College, Baldwin-Wallace College, Black Hills State University, Cedarville University, Defiance College, Graceland University, Howard Payne University, LeTourneau University, Montana State University Billings, Randolph-Macon College, University of Rochester, University of Wisconsin–Superior, West Virginia State University and Waynesburg University.
Notable secondary schools and school districts include Fort Mill High School (Fort Mill, SC) Franklin High School (Stockton, CA), Kingfisher High School (Kingfisher Oklahoma), Alvin High School (Alvin, TX) Sprayberry High School (Marietta, Georgia), Thomas County Central High School, (Thomasville, GA), Xavier University Preparatory High School (New Orleans, Louisiana), Berkeley High School (Berkeley, California), Freeport Area School District (Sarver, Pennsylvania), Ferndale Area High School (Johnstown, Pennsylvania), Llano High, Junior High, Elementary, and Packsaddle Elementary Schools (Llano County Texas), Cleburne High School (Cleburne, Texas), Mount Vernon High School (Mount Vernon, Ohio), Newark High School (Newark, Delaware), Osbourn Park High School (Manassas, Virginia), James Monroe High School (Fredericksburg, VA), Roane County High School (Kingston, TN), Sabinal School District (Sabinal, Texas), Perrysburg High School (Perrysburg, Ohio), Sidney High School (Sidney, Ohio), Girard High School (Girard, Pennsylvania), Vincent High School (Vincent, Alabama), McAdory High School (McCalla, Alabama), Thomas Jefferson High School (Council Bluffs, Iowa), Irmo Middle School, Irmo High School (Irmo, South Carolina) and Oxnard High School (Oxnard, California), Saint Augustine High School (Saint John's County FLA), Lee County Senior High School (Sanford, NC), Palo Verde Valley High School (Blythe, California), George Washington Carver High School (Winston-Salem, North Carolina) Northampton High School (Eastville, Virginia), Coffee High School (Florence, Alabama), Blue Ridge High School (Pinetop-Lakeside, Arizona), Sheridan School District (Sheridan, Arkansas), Oneonta High School (Oneonta, New York), Gwynn Park High School (Brandywine, Maryland), Ithaca High School (Ithaca, Michigan), Starkville High School (Starkville, Mississippi), St. Martin High School (St. Martin, Mississippi), Detroit Country Day School (Beverly Hills, Michigan), Woodford County High School (Versailles, KY), Luther Burbank Middle School (Burbank, CA) Oakleaf Junior High (Orange Park, FL), Spencer Middle School (Spencer, WV), and Colton High School (Colton, CA), Greenville High School (Greenville, MI), Bassfield High School(Bassfield, Mississippi), and Kermit High School (Kermit, TX)
Also has been used as the name of multiple superheroes, including the third superhero identity of Marvel Comics character Hank Pym; the villainess turned hero Rita Demara, who stole the identity from Pym; and YellowJacket, a Charlton Comics character who got his powers from being bitten by mutant yellow jackets. A fictional type of yellow jacket was used in The Hunger Games. They are called "tracker jackers," a genetically mutated species that's lethal to all people from repeated stings.
See also 
- German wasp, Vespula germanica
- Common wasp, Vespula vulgaris
- Biological pest control
- Volucella pellucens
- Akre, R.D. et al. (1980) The yellowjackets of America north of Mexico. USDA Agriculture Handbook 552. 102 pp.
- Lives of Social Insects Peggy Larson p13
- "Yellow jackets building enormous nests". TuscaloosaNews.com. Retrieved 2013-01-14.
- Extension Daily: What is Causing Super-sized Yellow Jacket Nests?
- "Response of Native Plant Communities to Alien Species Management on the Island of Hawaii" on the Hawaiian Cooperative Studies Program website