Yellowjackets (Vespula Wasps)

Vespula spp.
Family

Vespidae (a wasp family) in the order Hymenoptera (ants, bees, wasps)

Description

Yellowjackets are bee-sized social wasps that build paper nests, usually underground. They usually have beelike black and yellow bands on their abdomens, but unlike honeybees, they are not densely hairy, nor do they collect pollen. Yellowjackets have yellow or white faces. When resting, they usually hold their wings down their back (not spread out). Right before landing, they often fly quickly side to side.

Yellowjacket nests are made of paper like those of paper wasps, but they have multiple parallel layers of comb with downward-facing cells (paper wasps always only have a single layer of cells). Yellowjacket nests are always enclosed in a wood-pulp paper envelope built by the wasps.

Yellowjackets are widely, and incorrectly, called "sweat bees" in Missouri.

Yellowjackets are a significant stinging threat: They nest in colonies and aggressively defend their nest as a group. Individuals can sting repeatedly. Most people only experience localized pain when stung, but some people are severely allergic to wasp and bee stings, and they may experience life-threatening reactions (such as difficulty breathing) if stung. See "Human Connections" below for more information.

Similar species: The bald-faced hornet (Dolichovespula maculata) is closely related (in the same subfamily), but it is larger and is black with white or ivory-colored markings. They, too are social wasps that live in colonies. They build large, rounded, papery, gray nests, usually in trees.

Size

Length: about ½ inch (worker).

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Photo of large nest of southern yellowjacket
Southern Yellowjacket Nest

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Photo of an eastern yellowjacket
Eastern Yellowjacket
Habitat and conservation

Missouri's two statewide native species most often nest underground, having started the nest in a cavity such as a rodent burrow. Though there may be a large paper nest beneath the soil, all you might see is a hole with wasps flying in and out of it. Yellowjackets can also nest in trees, attics, and sheds. The non-native German yellowjacket prefers to build its nests in buildings, not underground, and as it spreads, more people will encounter that species.

Foods

All three species feed on a large variety of insects, including many that are injurious to crops, gardens, and landscaping. Larvae, in the nest, are fed such insects, which the adults collect and chew up for them. Yellowjackets also eat flower nectar, juices from fruits, and other sweets. Because they commonly feed from food scraps, soda cans, and garbage, foraging workers often get close to people and therefore pose potential stinging hazards.

image of Yellowjackets Distribution Map
Distribution in Missouri

Two native species occur statewide, the eastern yellowjacket (V. maculifrons) and southern yellowjacket (V. squamosa); the introduced German yellowjacket (V. germanica) is expanding its range and will eventually occur statewide, especially in urban areas.

Status

Common. As the summer progresses, nests increase in size and in the numbers of wasps they hold, becoming more conspicuous.

Life cycle

Social ants, bees, and wasps have been called "superorganisms" because the entire colony, and not just an individual creature, undergoes a reproductive life cycle of its own, and no single individual or even pair of individuals is enough to carry through the reproductive cycle; the entire colony is needed. This is one reason why social insects defend their nests so vigorously: each individual may give up its life to defend the whole colony, which shares its genetics and ultimate reproductive destiny.

On the "individual" level, each yellowjacket, like other ants, bees, and wasps, undergoes complete metamorphosis, similar to that of butterflies and flies. Eggs hatch into grublike larvae that scarcely resemble the adults. They eat and grow, sheltered within a cell of the paper nest, then pupate to become winged adults. Each larva and pupa, whether it is destined to become a female worker, a male, or a queen, matures within a cell of the wasp nest, tended by the worker adults.

The entire colony has its own life cycle: recently mated queens overwinter alone in a protected site such as under bark or in a wood pile. In spring the queen begins her nest and starts laying eggs, which hatch as female workers. The workers soon take over the colony’s tasks, allowing the queen to just lay eggs. The colony grows; by September it can contain 5,000 workers, all closely related daughters of the queen. Then the queen lays eggs for males and new queens. Once grown, these leave the nest and mate; the workers, original queen, and males die, and the newly fertilized queens hibernate.

Human connections

Yellowjackets hunt caterpillars, many of which are crop and forest pests, making yellowjackets distinctly beneficial to human interests.

Although these wasps do much that benefits humans, their capacity for colonial, defensive stinging makes them a major pest when they nest near people, especially since some people are allergic to bee and wasp venom. Signs of a severe allergic reaction may include swelling of the face, lips, or throat; breathing difficulties; hives or itching in areas not near the sting; sudden drop in blood pressure; dizziness or lightheadedness; nausea; or loss of consciousness. Also, if a non-allergic person is stung many times at once, it may be enough to produce a severe allergic reaction. If you think you are having a severe allergic reaction to a wasp sting, seek immediate medical help, including calling 911 or other emergency services, as you may not be able to drive yourself to a medical provider. If a doctor has prescribed for you an an emergency epinephrine autoinjector, use it right away, as prescribed.

Many people encounter yellowjacket nests when they are mowing a lawn and fail to notice the wasps flying in and out of the hole in the ground that is the entrance to their nest burrow. Before mowing, it's always a good idea to walk the area to look for rocks, sticks, trash, and the nests of animals (including yellowjackets)!

If you want to eliminate a yellowjacket nest, we recommend consulting a licensed exterminator.

Yellowjacket's love of sweets causes them to be attracted to soda cans. Sometimes people are stung on the lips when they sip soda out of a can that a yellowjacket is visiting.

People rightly fear yellowjackets and other social wasps that are capable of stinging en masse. But as with many animals that can powerfully affect humans, these wasps have earned a place of respect in our culture. Note, for instance, the many sports teams that are named "yellowjackets," "hornets," and so forth.

If yellowjackets seem unreasonably "mean," remember that they are defending their home and family from what their brains perceive as potential destruction. Many of us are prepared to do basically the same thing, on a personal and even a national level.

A closely related genus of wasps, Vespa, occurs in Eurasia, with one species, the European hornet (V. crabro) introduced to North America (including Missouri). Vespa means "wasp" in Italian, and it also happens to be the name of one of the world's most iconic makes of motor scooters, the Vespa by Piaggio.

Ecosystem connections

Yellowjackets are predators of caterpillars, including many species that are crop and forest pests.

Yellowjackets play a role in pollination.

The black-and-yellow striped pattern of yellowjackets warns predators not to mess with them! The coloration is easily memorized by animals after being stung. Once educated, those animals learn to avoid the wasps. It's a win-win for the yellowjackets and for the animals that have learned the painful lesson.

Yellowjackets are also connected with species that have evolved to have colors and patterns that "mimic" the black-and-yellow pattern of these stinging insects. Various species of flies and moths — completely incapable of stinging — are avoided by predators because of their resemblance to the stinging yellowjackets.

Yellowjackets are also connected to moles, voles, chipmunks, ground squirrels, shrews, snakes, and other animals that create, use, or reuse burrows in the ground. In a wider sense, all the burrowing animals are connected to trees that die and whose root systems are eaten away by fungi, creating the start of a hole for burrowing animals to utilize.

Skunks, raccoons, badgers, bears, and other mammals have been known to attack and destroy yellowjacket nests in order to eat the wasp grubs, eggs, and even adults. Skunks typically attack at night when the yellowjackets are least active, digging into the burrow, pawing through the nest, and eating the wasp larvae. Shrews and moles may eat yellowjackets as they burrow underground, too.