Dolichovespula maculata

The bald-faced hornet gets its name from the characteristic white markings on its face, as the word "bald" in English is derived from the word "piebald".[3] It was first described by Carl Linnaeus in his 1763 Centuria Insectorum. D. maculata is part of the cosmopolitan family Vespidae, in the genus Dolichovespula. Its black and white coloring differentiates it from its mostly black and yellow congenerics.[1]

The bald-faced hornet is distinguished from other yellowjackets by its striking black-and-white coloring. It has a white or "bald-faced" head, which is the source of its colloquial name. This wasp also has three white stripes at the end of its body and is notably larger than other species of Dolichovespula, as adults average about 19 mm (0.75 in) in length.[4] Queen and worker wasps have similar morphologies. Queens are always larger than workers in their colonies, though size distributions can vary in different nests, and workers in one colony might be as large as a queen in a different one.[1]

D. maculata creates egg-shaped, paper nests up to 360 mm (14 in) in diameter and 580 mm (23 in) in length. Nests are layered hexagonal combs covered by a mottled gray paper envelope. Bald-faced hornets create this paper envelope by collecting and chewing naturally occurring fibers. The wood fiber mixes with their saliva to become a pulpy substance that they can then form into place.[4]

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  Nest attached to a tree branch
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  Inside the paper covering of a bald-faced hornet nest are several suspended combs containing chambers for larvae.
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  This view, with paper outer wall removed, shows the final, small comb that hangs at the bottom.

Dolichovespula maculata distribution

The bald-faced hornet lives in North America, including Canada, the Rocky Mountains, the western coast of the United States, and most of the eastern United States. It is most common in the Southeastern United States.[3]

D. maculata is found in forested areas and in vegetation in urban areas. Nests are generally located in trees and bushes, but occasionally are found under rock overhangs or the sides of buildings. Vertical distribution of nests has been recorded from heights of 0.3 to 20 m (1 ft 0 in to 65 ft 7 in) above ground level.[5]

Bald-faced hornets are omnivorous, and considered to be beneficial due to their predation of flies, caterpillars, and spiders. Their aggressive defensive nature, though, makes them a threat to humans who wander too close to a nest or when a nest is constructed too close to human habitation. They vigorously defend the nest, with workers stinging repeatedly, as is common among social bees and wasps. The bald-faced hornet has a unique defense in that it can squirt or spray venom from the stinger into the eyes of vertebrate nest intruders. The venom causes immediate watering of the eyes and temporary blindness.[4]

The life cycle of a colony can be divided into the founding stage, the ergonomic stage, and the reproductive stage.[6] Colonies show annual cycling. New nests are generally founded during spring and early summer by a single queen, though temporal specifics vary depending on location. In Washington, nest initiation occurs during mid-May, and workers emerge during mid-June. Large-cell building starts during mid-July, and the first queens emerge during mid-August. The colony terminates during mid-September, for a life cycle around 4 months (122 days).[5] Lower latitudes correlate with longer life cycles. In Indiana, colonies have been observed to begin in early May and terminate in late September, a life cycle of 5 months (153 days), and in Central California, nests are initiated as early as the end of March. These nests survive between 155 and 170 days.[5] Active colonies have been observed in central Pennsylvania as late as mid-October. On October 28, 2022, an active colony was encountered on the Middle Fork Willamette River in western Oregon.

Diet in D. maculata varies depending on an individual's life cycle stage and geographic location. Adult yellowjackets, like true hornets, are carnivorous, and prey upon several insect types. They have been observed consuming meat, spiders, fruit, and insects. Adults also drink flower nectar, which they feed to their larvae.[10]

Female bee moths (Aphomia sociella) have been known to lay their eggs in bald-faced hornet nests. The hatched larvae then proceed to feed on the eggs, larvae, and pupae left unprotected by the wasps. This infestation can destroy large parts of the nest as the larvae tunnel throughout it looking for food.[11]

Each spring, queens that matured and were fertilized at the end of the previous season begin new colonies. A queen selects a location for her nest, begins building it, lays a first batch of eggs, and feeds this first group of larvae. These become workers and assume the chore of expanding the nest. They chew up wood, which mixes with a starch in their saliva. They then spread it around with their mandibles and legs, and it dries into a papery structure. The workers guard the nest and feed on nectar, tree sap and fruit pulp (particularly that of apples). They also prey on insects and other arthropods, chewing them up and feeding them to the larvae. They have been known to scavenge raw meat. In late summer and early fall, the queen begins to lay eggs that become drones and new queens. After pupation, these fertile males and females fly off to mate. Fertilized queens then overwinter and start new colonies during the next year. Males and workers die in the end of the cycle. The old queen, if not killed by workers, dies with them around mid-autumn.

Wikimedia Commons has media related to Dolichovespula maculata.

• Bald-faced hornet at PestWorld.org
• Bald-faced hornet at Hornets: Gentle Giants
• Bald-faced hornet at Study of Northern Virginia Ecology. Fairfax County Public Schools, VA