Overview
The bald-faced hornet (Dolichovespula maculata) is the most visually striking and most aggressive stinging insect in Quebec. Despite its name, it is technically a yellow jacket, not a true hornet. It builds large, football-shaped paper nests in trees, on structures, and under eaves. Colonies reach 400–700 workers by late summer and will aggressively defend the nest against any perceived threat. Professional removal is strongly recommended for any nest larger than a tennis ball.
How to Identify Bald-Faced Hornets
- Size: 15–20 mm long — larger than yellow jackets
- Colour: Black with distinctive white (ivory) markings on the face, thorax, and abdomen tip
- Nest: Large, football-shaped paper nest — grey, with a layered, papery exterior
- Nest location: Hanging from tree branches, eaves, utility poles, and other elevated structures
- Flight: Fast and direct; workers patrol a large area around the nest
- Aggression: Extremely aggressive when the nest is disturbed — will pursue threats for considerable distances
Biology & Colony Development
- Colony founding: Single overwintered queen emerges in May and begins building a small nest
- Colony growth: Rapid expansion from May through August
- Peak colony size: 400–700 workers by late summer
- Nest size: Golf ball in May; football or larger by August
- Diet: Protein (insects) in spring/summer; sugar in late summer
- Colony decline: Workers die off in October; new queens overwinter in protected locations
- Nest reuse: Old nests are never reused
Health Risks
- Stings: Extremely painful — bald-faced hornets can sting repeatedly
- Venom injection: Can spray venom into the eyes of perceived threats, causing temporary blindness
- Anaphylaxis: 1–3% of the population is allergic to wasp venom; anaphylactic reactions can be fatal
- Mass attack: A disturbed colony can deploy hundreds of defenders simultaneously
- Pursuit: Workers will pursue threats for 50+ metres from the nest
Signs of Infestation
- Visible nest: Large, grey, football-shaped paper nest hanging from a tree, eave, or structure
- Worker activity: Large black and white wasps flying in and out of the nest entrance at the bottom
- Increased activity: Large numbers of bald-faced hornets in a specific area of the yard
- Nest construction: In May–June, a small founding nest (golf ball size) may be visible before it grows large
Prevention
- Inspect trees, eaves, and outbuildings in early spring (April–May) for founding queens and small nests
- Remove small founding nests immediately — they are easy to treat when small
- Seal gaps in soffits, fascia, and exterior walls where queens might enter
- Trim dense vegetation that provides sheltered nesting sites
- Keep outdoor garbage bins sealed
Professional Treatment
Professional bald-faced hornet removal requires full protective equipment. A fast-acting insecticide is applied directly to the nest entrance, killing workers as they enter and exit. The nest is then physically removed and disposed of. Treatment is performed at dusk when workers are least active. NEVER attempt DIY removal of a bald-faced hornet nest — the colony will mount an immediate, aggressive defence that can result in dozens or hundreds of stings.