Despite being called a "hornet," the bald-faced hornet (Dolichovespula maculata) is actually a large yellowjacket wasp — and one of the most aggressive stinging insects in Montana. Recognizable by their striking black-and-white coloring and their remarkable paper nests, bald-faced hornets are a force to be reckoned with when their colony is disturbed.
Colonies begin each spring when an overwintering queen selects a site and begins building the distinctive gray, papery nest — constructed from chewed wood fibers mixed with saliva. By late summer, a mature nest can be the size of a basketball or larger, containing 400–700 workers, and may hang from tree branches, under eaves, on utility poles, inside shrubs, or in any sheltered elevated location.
Unlike yellow jackets, bald-faced hornets are not typically attracted to food or trash — they are aerial predators, hunting flies, other wasps, and insects to feed their larvae. This makes them somewhat ecologically valuable. However, when nesting near human activity, their defensive nature makes them dangerous. They will pursue perceived threats for significant distances and, like yellow jackets, can sting multiple times.
Size
¾ inch (large)
Color
Black with white facial and abdominal markings
Active Season
April–October; nests peak August–September
Risk Level
High (aggressive; multiple stings; anaphylaxis risk)
Habitat
Aerial nests in trees, under eaves, in shrubs
Colony Size
400–700 workers
SIGNS OF INFESTATION
Identifying a Bald-Faced Hornet Nest
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Visible paper nest — A large, gray, teardrop-shaped paper nest hanging from a tree, eave, beam, or shrub is unmistakable.
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Increased large wasp activity — Large black-and-white wasps flying in and out of a specific area in a purposeful, repeated pattern.
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Nest in dense vegetation — Nests in hedges or bushes are harder to see; discover them the hard way when mowing or trimming, or spot them during winter when foliage drops.
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Workers hunting in the yard — Bald-faced hornets actively hunt other insects; seeing large wasps patrolling your garden indicates a nearby colony.
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Audible buzzing from above — A low, constant buzzing from eaves, a roof overhang, or a nearby tree can indicate an active nest.
HEALTH RISKS
Bald-faced hornets are among the most defensive stinging insects in Montana. They will sting with little provocation within 3 feet of their nest, and a disturbed colony will send dozens of workers to pursue a threat. Their venom is potent and multiple stings can be dangerous even for non-allergic individuals. For those with venom allergies, a single sting can trigger anaphylaxis. Their tendency to aim for the face — targeting the eyes and mouth — makes encounters particularly dangerous. Never attempt to remove a bald-faced hornet nest yourself.
PROPERTY DAMAGE
Bald-faced hornets cause no structural damage. However, nests built inside wall voids, attics, or under siding (which does occasionally happen) can be a problem when the colony dies and the nest is left to decay — attracting other pests and potentially causing moisture issues.
