Social Wasps: Yellowjackets, Hornets, and Paper Wasps

Diet 

• Adult wasps consume a liquid diet and are attracted to sugary substances. They feed on flower nectar, fruit juices, oozing sap, honeydew excreted by sap-feeding insects, and nutritional liquids produced by their young.
• Insects, other invertebrate prey (such as spiders or worms), and carrion (dead animals) are scavenged or hunted by adult wasps as food for their young (larvae). Captured food is typically chewed into smaller pieces and then flown back to the colony. Although adults might ingest juices from the prey item, it is not the primary food source of adults.

Nesting  

• Nests are built out of a paper-like material that wasps make using chewed-up wood pulp and saliva. This material forms the brood cells (the honeycomb-shaped structure the larvae live in) and the nest envelope (covering). Worker wasps enlarge the nest with additional comb and paper layers as the colony grows. Pulp from different wood sources can result in paper bands of a different color.
• Nests are located in sheltered hollows (such as tree cavities or wall voids), under building eaves or tree branches, or in the ground (such as in an old rodent burrow), depending on the wasp species. They do not excavate nesting sites, but find and utilize pre-existing locations that suit their needs. Wasps that nest in trees do not cause the tree significant damage, but the collection of nesting material may injure a few branches.
• The nest population grows in number throughout the season, with only a handful of individuals in spring and potentially hundreds by autumn. All nest members are female until the colony is ready to reproduce.

• Spring: As the weather warms, reproductive females, called queens, emerge from a hibernation-like state and search for a suitable nest site. Each wasp queen works alone and begins nest construction and raising the first generation of workers by herself. All worker wasps are sterile females.
• Summer: Workers take over nest construction duties as well as foraging for food, and the queen remains in the nest to lay eggs for future generations of workers. The nest population gradually increases until it reaches its largest number of wasps by late summer or early autumn.
• Late summer into autumn: Some of the larvae raised become new queens and males instead of workers, and they leave the nest to find mates. Males die soon afterward, while the queens search for a sheltered location to overwinter by themselves, such as under a fallen log or in a tree crevice. The social order of the nest may begin to break down, and the workers might be more easily agitated and defensive of a disturbed nest.
• Winter: Freezing weather ends any remaining nest activity. The original queen from spring, all of the female workers, and all of the males die. Young mated queens have left the nest and are inactive, overwintering elsewhere (leaf litter, tree bark, compost piles, logs, soil cavities, wall voids). The nest will not be re-used.

European hornet (Vespa crabro) 

This is the only true hornet established in the U.S. They are non-native, but have lived in North America for over a hundred years.

Identification

• Relatively large among social wasps, ranging from ¾ to 1 ⅜ inches long. Due to size, it might be mistaken for a Northern giant hornet or the eastern cicada killer wasps. 
• Body colors are brick-hued reddish-brown with golden yellow on the abdomen and face, with darker markings on the thorax and abdomen. Teardrop-shaped marks on the abdomen are distinctive.

Nest traits

• Usually tan-brown in color and relatively fragile.
• Located in concealed sites, such as hollow trees, barns, outbuildings, wall voids, attics, and abandoned honey bee hives.
• At peak population, most nests may contain about 200 to 400 workers; larger nests can contain over 1,000 workers.

Notable behavior

• Often observed preying on other pollinators by hunting around flowering plants. Prey can include grasshoppers, flies, and bees, as well as other wasps, plus a variety of additional species.
• Can fly both day and night. Like many night-active (nocturnal) insects, this wasp may be attracted to outdoor lights (porch lights, landscape accent lighting, and light leaking through window blinds or curtains) and can accidentally collide with windows as a result. They may also be attracted to light from a flashlight.
• Chews bark off of young tree or shrub branches in order to cause sap to flow. May ingest the sap directly, catch insects drawn to the sap, and/or use the wood pulp for nest building. Common targets include lilac, viburnum, rhododendron and birch. If extensive girdling (damage to sapwood encircling the branch) occurs, the branch may die back to that point, but overall, shrubs and trees are usually not seriously harmed by hornet activity.

Baldfaced hornet (Dolichovespula maculata)

Despite its common name, this is a type of “aerial” yellowjacket (one of 7 to 8 such species in North America), not a true hornet. They are native to the U.S. and widespread in Maryland.

Identification

• Medium-sized among social wasps, ranging from ⅝ to ¾ of an inch long for workers and just over an inch for queens.
• Body colors are black and white, with a white face.

Nest traits

• Usually light gray in color, but may include a mix of gray and light brown stripes.
• The main entrance is the lowest and most prominent opening in the cone- or egg-shaped nest, but other arched openings around the top of the dome also give wasps access to the interior. A relatively new nest may have a long entrance tube extending downwards.
• Nests are built out in the open, with combs surrounded completely by a paper envelope. They can be surprisingly easy to miss, given their eventual size, until winter reveals their presence. Nests may hang from a tree branch, potentially up to 60 feet or more high in the canopy, or be attached at least 3 feet high to a building overhang, wall, or utility pole.
• At peak population, nests may contain about 100 to 400 workers.

Northern giant hornet (Vespa mandarinia)

In the United States, this non-native hornet has not been found outside of Washington state. This wasp is native to Asia but was first found in British Columbia, Canada, and in Washington State in the fall and winter of 2019. Washington set up a baited trap system for surveying populations of this pest, and occasional isolated detections of additional hornet individuals or nests have occurred in the years following. Located nests are eradicated.

Given their large size, European hornets (social wasps) and Eastern cicada killers (solitary wasps) are often misidentified as this species. If you think you have found this hornet outside of Washington, it is likely one of the similar species above. After reviewing the identification materials on this page, if you think you have encountered a Northern giant hornet, please send a photo of the wasp to your local Extension office or submit it to Ask Extension.

Identification

• The largest hornet in the world, ranging from 1½ - 2  inches long for workers and  up to 2¼ inches long for queens.
• Body colors are golden-yellow, black, and dark brownish-black. The head is entirely yellow and the dark banding on the abdomen lacks the teardrop or triangular-shaped markings present on the European hornet.

Nest traits

• Nests are typically made underground in abandoned rodent burrows or sometimes in dead, hollow tree trunks or hollows between roots. Aerial nests are rare.
• At peak population, nests may contain about 300 or more workers.

Notable behavior

• Workers are usually solitary hunters, but may team-up to attack other social wasp nests or honey bee hives, especially later in the season when workers are abundant.
• Has a reputation for preying on honey bee colonies.
  • Northern giant hornets have three different attack phases: hunting phase, slaughter phase, and occupation phase. What triggers this shift in behavior (attack phases) is still unknown. 
  • During the hunting phase, hornet workers will catch and kill individual bees (mainly guard bees and scouts) outside the hive. They pull apart the bee to access the thorax (the body segment powering wings and legs) because it is a rich energy source for the hornet larvae. If a honey bee nest is found, the hornet will scent-mark the nest to potentially return with more workers at a later time.
  • During the slaughter phase, multiple worker hornets will target one particular honey bee hive. In this phase, up to 50 hornets will wait near the entrance of the hive and will bite to death each bee that approaches them. Unlike other attacks, they will not take any part of these bees back to their hive, but will drop the killed bee and wait for the next one. 
  • Once the attacked honey bee hive is defeated, the occupation phase begins where the hornets will enter the hive and raid the comb; taking the protein-rich parts of the bee pupae and larvae back to their nest. Honey is rarely taken back to the hornet nest. Hornets will guard the honey bee hive from other hornets, people, and animals while taking resources back to their nest.
• Despite the sensationalized nickname “murder hornet,” Northern giant hornets are typically not aggressive toward humans, but will sting if handled or defending a nest. Use extreme caution near northern giant hornets. Like other hornets and wasps, they can sting multiple times.
• A Northern giant hornet sting is described as being extremely painful, due to stinger size and the volume of venom delivered per sting. However, it is not clear if they are more likely to cause death or induce an allergic reaction than honey bees, yellowjackets, and other social wasps.

Yellow-legged hornet (Vespa velutina)

This non-native hornet has not been found in the Mid-Atlantic region. The first detection of this species in the U.S. was in Savannah, Georgia, in August 2023, followed by another in South Carolina in November 2023. Their native range is tropical and subtropical areas of Southeast Asia, though they were accidentally introduced to Europe in the early 2000s. As per routine procedure for new and potentially invasive species, the United States Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) is working with the Georgia Department of Agriculture, the University of Georgia, and Clemson University to identify, trap, track, and eradicate these hornets.

European hornets might be misidentified as this species due to their similar size and coloration. If you think you have encountered a yellow-legged hornet, please send a clear photo of the wasp to your local Extension office or submit it to Ask Extension.

Identification

• Somewhat large among social wasps, ranging from 3⁄4 to 1¼ inches long for queens. Early-season workers are relatively small at about ½ inch, with later generations nearing the size of a queen by the end of the season. 
• Body colors are variable (multiple color morphs exist), but only one color morph (form) has been introduced outside of Asia. This introduced color morph is primarily a mix of near-black and golden-yellow. The face is yellow; the rest of the head is black. Lacks the distinctive teardrop-shaped markings on the abdomen of the European hornet. The lower portions of the legs are yellow.

Nest traits

• The nest is similar in appearance to that of a baldfaced hornet.
• Nests are built out in the open, hanging from a tree branch, with combs surrounded completely by a paper envelope.
• Two nests are built during the course of a growing season. The first is more irregular in shape and houses only the first generations of workers the queen produces. Later in summer, the colony builds and moves into a separate secondary nest which is usually higher off the ground and the typical egg shape.
• At peak population, nests may contain about 400 workers. In its native range, where the climate is warmer, populations for a single nest can average thousands of workers.

Notable behavior

• Uses a “bee hawking” behavior similar to the predation on honey bees of the Northern giant hornet. Prey preference includes bees, other wasps, and flies. Workers may hunt around pollinator-attracting flowers, near honey bee hives, or around dead animals that attract flies.