What Is the Difference between Wasps and Hornets?

Ask most Ontario homeowners what stinging insect is nesting under their eaves and they may commonly answer with 'wasps' and the occasional 'hornets'. Ask a pest control technician, we will answer with lecture about how wasp and hornet are not the same thing. There are difference between them determines how dangerous the nest is, how large it will grow, and what it takes to treat it safely.

This guide covers every stinging insect species found in Ontario homes and yards, what separates wasps from hornets, how to identify which one you're dealing with, and exactly what that identification means for the treatment approach.

The biological distinction between Wasps and Hornets

The word 'hornet' is commonly used as a catch-all for any large, aggressive stinging insect. Actually it's all hornets are wasps (Vespidae family) but not all wasps are hornets. Hornets are a subgroup within the broader wasp category, distinguished by their larger body size, different nesting behaviour, and significantly greater colony aggression.

In practical terms for Ontario homeowners:

• Wasps: Yellowjackets (Vespula spp.), Paper Wasps (Polistes spp.), and Mud Daubers (Sceliphron caementarium)
• Hornets: Bald-Faced Hornets (Dolichovespula maculata) and European Hornets (Vespa crabro)

Bald-faced hornets are technically classified by entomologists as a Yellowjacket species rather than a true hornet. In pest control practice, they are treated as hornets because their size, nest type, and aggression profile match the hornet category far more closely than a Yellowjacket.

All Ontario Stinging Insect Species Comparison

Yellowjackets — THE MOST DANGEROUS ONTARIO SPECIES

Yellowjackets (Vespula germanica and Vespula vulgaris) are the species behind the vast majority of serious stinging incidents in Ontario. They are highly aggressive social wasps that defend their territory actively — not just when the nest is disturbed, but when they perceive any threat in a radius of several metres.

Key identification features:

• Body length 12–15mm — smaller than a hornet
• Bright yellow and black banding on the abdomen, no hair
• Slender waist (petiole) clearly visible — more pinched than a bee
• Smooth, shiny body surface
• Fly with legs held close to body, not dangling

Nest type and location:

Yellowjackets build papery nests from chewed wood fibre mixed with saliva. They nest in three primary locations in GTA homes and yards:

1. Underground in abandoned rodent burrows or soft soil
2. Inside wall voids and attic spaces (entering through small gaps in siding or mortar)
3. Occasionally in aerial locations under eaves or in dense shrubs

Underground and wall void nests are the most dangerous because the colony is completely enclosed and the entrance is often not visible until it is stepped on or disturbed.

Why Yellowjackets are the highest-risk species:

A Yellowjacket colony at peak season (late August and September) can contain 3,000 to 15,000 workers. Individual workers can sting multiple times without dying. When a colony is disturbed, the alarm pheromone released by the first few stings triggers a rapid mass mobilisation of the worker population with hundreds of workers responding within seconds. People who accidentally step on or near an underground nest have reported receiving dozens of stings before they were able to move away.

Late summer aggression increases significantly as food sources diminish and the colony concentrates on nest defence. A Yellowjacket nest that was relatively unobtrusive in June becomes a genuine safety hazard by August.

Bald-Faced Hornets — THE AERIAL THREAT

The Bald-Faced Hornet (Dolichovespula maculata) is the most visually distinctive stinging insect in Ontario. It is large, black-and-white, and capable of building football-to-basketball-sized aerial nests in trees, on building exteriors, and under deck structures.

Key identification features:

• Body length 15–20mm — noticeably larger than Yellowjackets
• Predominantly black with distinctive white markings on the face and tail
• Larger, more robust body than Yellowjackets or Paper Wasps
• Aerial paper nest is unmistakable — grey, enclosed, teardrop to football shape

Nest type and location:

Bald-Faced Hornets build large enclosed papery nests attached to tree branches, building eaves, fence posts, and the underside of decks. Nests begin golf-ball size in May and grow to football or basketball size by August which can contain between 400 to 700 workers at peak. Unlike Yellowjacket aerial nests, bald-faced hornet nests are always fully enclosed with a small entrance hole at the bottom.

Why they require professional treatment:

Bald-Faced Hornets are among the most aggressive stinging insects in North America when their nest is approached. Their defence radius extends several metres. People have been stung simply walking too close to a nest without touching it or the branch it's on. This defence radius makes DIY treatment genuinely dangerous: by the time you are close enough to apply a consumer spray, you are already within the zone where workers will respond.

European Hornets — THE LARGE NOCTURNAL SPECIES

The European hornet (Vespa crabro) is Ontario's only true hornet by strict entomological definition, it is the largest stinging insect spanning 25 to 35 mm that most GTA homeowners will ever encounter.

Key identification features:

• Body length 25–35mm — significantly larger than any other Ontario stinging insect
• Brown and orange colouring with yellow abdominal banding — distinctly different from Yellowjacket's bright yellow and black
• Workers are active at night as well as during the day — the only Ontario stinging species with nocturnal flight
• Attracted to lights at night, which is when homeowners most often see them indoors

Nest type and location:

European hornets nest in enclosed cavities: tree hollows, wall voids, attic spaces, and old outbuildings. Unlike Yellowjackets, they rarely nest underground. The nest itself is made of the same papery material as Yellowjackets and bald-faced hornets, but is typically found inside a cavity rather than exposed in the open. Mature European Hornet colonies contain 200 to 400 workers.

Aggression profile:

European hornets are less likely to sting unprovoked than Yellowjackets, but they are still capable of multiple stings and will defend the nest aggressively if it is disturbed. Their large size makes individual stings more physically impactful than those of smaller species. Wall void nests in particular should not be treated without professional equipment.

Paper Wasps — THE MOST COMMON EAVE DWELLER

Paper wasps (Polistes fuscatus and related species) are the most frequently encountered stinging insect on GTA residential properties. They build the characteristic open-comb umbrella-shaped nests that most homeowners recognise on their eaves, under deck boards, and on fence posts.

Key identification features:

• Body length 12–16mm, elongated and slender
• Reddish-brown to dark brown with yellow markings
• Distinctively long legs that dangle visibly in flight
• Open-comb nest with visible cells — not enclosed like Yellowjacket or hornet nests

Why Paper Wasps are lower risk:

Paper wasps are significantly less aggressive than Yellowjackets or bald-faced hornets. A small early-season nest under 30 workers found in spring can generally be knocked down at night with a consumer aerosol spray with acceptable risk. The caveat: by August, a large established paper wasp colony under a frequently used eave or deck board can produce a painful defensive response when the nest is accidentally disturbed during normal property use. A colony found in high-traffic proximity should be treated professionally.

Mud Daubers — NOT A THREAT

Mud daubers (Sceliphron caementarium) are solitary wasps that build distinctive clay or mud tube structures on walls, under overhangs, and inside garages and sheds. They are not a stinging threat because mud daubers are non-aggressive, do not have a colony to defend, and essentially never sting humans unless physically handled. The mud tubes are harmless and can be removed by hand.

If you have mud tubes on your exterior walls, the correct action is physical removal of the dried mud, not pesticide treatment. If mud daubers are a recurring issue, homeowners should seal gaps in siding and garage doors eliminates the sheltered surfaces they prefer for nest-building.

A Quick Guide to How to Tell Wasps and Hornets Apart

When you see a stinging insect or a nest, these six questions identify the species within seconds:

• Is the nest aerial and fully enclosed (grey, football to basketball shaped)? → Bald-faced hornet
• Is the nest open-comb and umbrella-shaped, visible cells, under eaves or deck? → Paper wasp
• Are clay/mud tubes on a wall or structure? → Mud dauber. Not dangerous. Remove by hand.
• Is it very large (25–35mm), brown/orange, active at night near lights? → European hornet
• Is the nest underground or inside a wall void, with wasps entering and exiting a small hole? → Yellowjacket. Highest risk. Call a professional.
• Is the nest in a tree or on a structure, large, enclosed, black and white insects? → Bald-faced hornet. Call a professional.

When DIY is Feasible and When to Call A Pest Management Professional

DIY for Wasps and Hornets is reasonable for:

• Small paper wasp nests under 30 workers found in May or early June and treated at night with a consumer jet-spray aerosol from 3+ metres distance
• Mud dauber tubes removed physically, no pesticide needed

Always call a Pest Management Professional for:

• Any Yellowjacket nest  regardless of estimated size and placement (ground, wall void, or aerial)
• Any bald-faced hornet nest — regardless of size or location
• Any European hornet nest — large size and wall void location require professional equipment
• Any nest where a household member has a known or suspected venom allergy
• Any nest in a wall void — do not block the entrance before treatment. Blocking traps the colony inside and forces workers to chew through interior surfaces into living spaces
• Any nest larger than a golf ball in August or September — colonies are at peak worker count and maximum aggression

Greater Toronto Area Seasonal Wasp and Hornet Timing

• April–May: Queens emerge from overwintering and establish new nest sites. A nest found in May contains 1 queen and 20–50 workers. Easiest and lowest-risk treatment window.
• June–July: Colonies grow rapidly. Yellowjacket and bald-faced hornet nests reach 500 to 2,000 workers. Paper Wasp nests reach peak for the season.
• August–September: Peak colony size and maximum aggression. Yellowjackets at 3,000–15,000 workers. Bald-faced hornets at 400–700. Highest sting-risk period. DIY attempts most likely to fail and cause injury.
• October–November: Worker populations die off with frost. New queens overwinter individually. Nests are not reused the following year but the same site is often reoccupied by a new queen if entry points are not sealed.