Vespa crabro Linnaeus, 1758

European hornet

Ontario's largest social wasp, brown and yellow, active at night, humming around porch lights in late summer.

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

Why it matters

Intimidating size and painful sting; nests in structures need professional attention. Predatory on insects, including honeybees at hive entrances in late season. Not aggressive without provocation at the nest.

Origin

Native to Europe and Asia; introduced to eastern North America in the 1800s, now established in Ontario.

Behavior

The only common Ontario wasp active at night, workers fly to porch lights after dark. Forages for insects, tree sap and fallen fruit. Less aggressive away from the nest than its size suggests, but the nest is vigorously defended and the sting is memorable.

Living conditions

Nests in hollow trees, wall voids, barns and sheds, large cavities. Needs mature trees and undisturbed voids.

Signs of presence

Very large wasps (20-35 mm) around lights at night in late summer
A deep, loud buzzing unlike smaller wasps
Traffic at a tree hollow or wall void

Weaknesses

Nocturnal habit makes it avoidable, turn off outdoor lights near seating areas
Single-season colonies; winter ends the nest
Nests in cavities, so exclusion (sealing voids) prevents establishment
Forages widely; it is not tied to your garbage like yellowjackets

Myths and facts

Myth Three stings can kill a person / they're the 'murder hornet'.
Reality European hornets are not the Asian giant hornet (Vespa mandarinia, not established in Ontario). Their sting is painful but the venom is comparable to other wasps, the danger is allergy and multiple stings, not a super-venom.

Research notes

Morphology

Workers 20-25 mm; queens to 35 mm. Reddish-brown thorax, yellow-and-brown banded abdomen, brown where yellowjackets are black. Large head with powerful mandibles. Nests: large paper combs inside cavities (hollow trees, wall voids), brownish envelope.

Diagnostics

Confirm by: 20-35 mm, reddish-brown and yellow (not black), nocturnal flight to lights, cavity nesting.

Easily confused with

Bald-faced hornet, Dolichovespula maculata Bald-faced hornets are black-and-white and build hanging aerial nests; European hornets are brown-and-yellow and nest inside cavities.
Asian giant hornet, Vespa mandarinia (not in Ontario) V. mandarinia is larger still (queens to 50 mm) with an orange head; any suspected specimen in Ontario warrants reporting, but all records to date are V. crabro.

Life cycle

Egg: Queen initiates the cavity nest in spring
Nymph or larva: Larvae fed masticated insects and sap
Adult: Colonies reach several hundred workers; active into the night, unusual among vespids; only queens overwinter
Egg to adult: Approximately 4-5 weeks per worker generation
Generations per year: One colony cycle per year

Development

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

Reproduction

Single foundress; autumn mating of new queens; colony dies with frost.

Distribution

Native range: Europe and temperate Asia
Ontario: Established, most common in the south; expanding with mature suburbs
Global: Eurasia; introduced eastern North America

Ecology

Cavity nester; strips bark for paper pulp (damaging young trees ornamentally). Predatory on flies, caterpillars and honeybees; also takes sap and fruit. Nocturnal foraging is exceptional among social wasps and reduces competition.

Resistance

Not applicable, no insecticide resistance documented.

IPM implications

Cavity-nesting biology means prevention is structural: seal tree hollows near homes, screen vents, close wall voids. Active nests in structures require professional treatment (night work, full protection, large colony, powerful stings). Light management (yellow 'bug lights', lights off near doors) reduces nocturnal encounters. As with all annual vespids, winter ends the colony.

Chemical ecology

Foraging guided by visual and olfactory cues; nocturnal activity suggests reduced reliance on vision vs. diurnal vespids, an open research area.

Genetics and DNA

No reference genome published as of 2026.

Taxonomy

Hymenoptera: Vespidae. Vespa crabro Linnaeus, 1758. A true hornet (genus Vespa); the largest eusocial wasp in Ontario.

Open questions

Northward range dynamics in Ontario; nocturnal foraging energetics and sensory basis.

References

Archer, Vespa crabro biology, primary literature
Evans & Eberhard (1970), The Wasps (Univ. Michigan Press)
Ontario apiculture resources, hornet predation at hives