Dolichovespula maculata Linnaeus, 1763

Bald-faced hornet

Big black-and-white wasps in hanging paper footballs, fierce at the nest, useful predators away from it.

Order: Hymenoptera
Family: Vespidae
Group: Wasps, hornets & bees
Ontario status: Established, native

Why it matters

The most defensive common wasp in Ontario near its nest, multiple painful stings, allergy risk. But ecologically valuable: each colony removes thousands of flies and caterpillars. Nests away from human traffic are best left alone.

Origin

Native across North America, from coast to coast.

Behavior

Hunts flies, caterpillars and other yellowjackets to feed its young, a beneficial predator. Extremely defensive within a few metres of the nest; will pursue intruders. Away from the nest, not aggressive.

Living conditions

Builds large grey paper nests hanging from tree branches, shrubs, and building eaves, the classic 'paper football', sometimes basketball-sized.

Signs of presence

A large grey papery nest hanging in a tree or under an eave
Big black-and-white wasps patrolling a fixed flight path to the nest
Increased wasp traffic after lawn equipment vibrates nearby

Weaknesses

Defence is nest-centred, away from the nest they want nothing to do with you
Single-season colonies; winter kills the nest
Nests are conspicuous and locatable
Queens found alone in spring

Myths and facts

Myth They're true hornets and will chase you for blocks.
Reality They're aerial yellowjackets, not true hornets. They defend a zone around the nest, usually a few metres, not the neighbourhood.

Research notes

Morphology

Workers ~12-20 mm; queens to ~25 mm. Black with ivory-white markings: white face ('bald-faced'), white-tipped abdomen. Builds enclosed aerial paper nests with a layered envelope, grey, football-shaped, single entrance at the bottom.

Diagnostics

Confirm by: 15-20 mm black-and-white (not yellow), white face, large hanging enclosed paper nest.

Easily confused with

European hornet, Vespa crabro European hornets are larger, brown-and-yellow (not black-and-white), and nest in cavities, never in hanging paper footballs.

Life cycle

Egg: Queen builds the first comb and lays eggs in spring
Nymph or larva: Larvae fed chewed prey (flies, caterpillars, other wasps) by workers
Adult: Colony peaks at a few hundred workers in late summer; only mated queens overwinter
Egg to adult: Approximately 3-4 weeks per worker generation
Generations per year: One colony cycle per year

Development

Complete metamorphosis: egg → larva → pupa → adult. Annual eusocial colony.

Reproduction

Single queen founds; autumn rears males and new queens; colony dies with frost.

Distribution

Native range: North America
Ontario: Common throughout; nests conspicuous from midsummer
Global: North America

Ecology

Aerial nester in trees, shrubs and on structures. Predatory, significant consumer of flies (including house flies) and caterpillars; also scavenges. Smaller colonies than ground yellowjackets (hundreds, not thousands) but more aggressive per capita near the nest.

Resistance

Not applicable, no insecticide resistance documented.

IPM implications

Risk-based decision: nests high in trees away from traffic are a net benefit (fly and caterpillar predation) and best left until winter kills them. Nests on structures, at doorways, or near play areas warrant professional removal, ideally at night when the colony is home, by licensed operators with protective equipment. The single-season biology means 'wait until winter' is a legitimate strategy for low-risk nests.

Chemical ecology

Nestmate recognition and alarm pheromones; prey location primarily visual.

Genetics and DNA

No reference genome published as of 2026.

Taxonomy

Hymenoptera: Vespidae. Dolichovespula maculata (Linnaeus, 1763). An aerial-nesting yellowjacket; 'hornet' is a common name, not a taxonomic rank here.

Open questions

Prey spectra in Ontario urban vs. rural colonies; overwintering site selection by queens.

References

Akre et al., Dolichovespula biology, primary literature
Evans & Eberhard (1970), The Wasps (Univ. Michigan Press)
Penn State Extension, bald-faced hornets