How a wasp builds a paper castle.

Notes on wasp nest engineering and the Quebec colony cycle, from spring queen to autumn collapse.

A wasp nest is, structurally speaking, a remarkable thing. It is built from material the wasp manufactures on the spot, using only what is available within a few metres of where she works. The material is paper. The wasp makes it the same way humans first made paper — by chewing wood fibres into pulp and binding them with saliva. The result is light, strong, water-resistant on the outside, insulated on the inside, and shaped by an insect with no blueprint, working alone, in a window of about three weeks.

The species you are likely to meet

In Quebec, the wasps that show up around buildings fall into three working categories. Paper wasps (Polistes) build small open-comb nests under eaves and patio furniture. Yellowjackets (Vespula and Dolichovespula) build closed paper envelopes, sometimes underground, sometimes in wall cavities, sometimes hanging from tree branches. Bald-faced hornets (Dolichovespula maculata) are technically yellowjackets despite the name; they build the large football-shaped grey nests that hang exposed from branches and eaves.

All three are eusocial. All three have a single annual cycle in our climate. All three build with paper. And all three will defend their nest with focused aggression if they perceive a threat — which is the part that most concerns most people.

How the nest is actually built

The queen who founds the colony arrives at her chosen site in spring, alone. She has no workers yet. She finds weathered wood — an old fence post, a deck rail, a tree stump — and scrapes the surface with her mandibles, producing a slurry of wood fibre mixed with her saliva. She flies the pulp back to the nest site and applies it to a surface, shaping it with her legs and mandibles as it dries.

The first thing she builds is a small stem, called a petiole, which anchors the nest to the substrate above. From the petiole she hangs a single hexagonal cell, then another, then a small cluster. Into each cell she lays one egg. By the time the first worker hatches, she has built perhaps a dozen cells and laid eggs in all of them. From this point, the workers take over construction and brood care, and the queen does nothing but lay eggs.

The construction proceeds outward and downward. The workers add layers of paper around the original comb, building an envelope that insulates the brood and protects against rain. They add new combs below the first one, separated by thin paper struts. By August, the inside of a yellowjacket nest may contain six or seven horizontal combs stacked vertically, each with thousands of cells, all enclosed by a multi-layered paper envelope with a single small entrance.

Why the entrance is small

This is a design choice. A small entrance is easier to defend. It limits airflow, which helps thermoregulation. It restricts the rate at which intruders can attack the colony. The size of the entrance scales with the colony — a young nest has a tiny entrance that workers expand as the colony grows. A mature yellowjacket nest in a wall cavity may have an entrance the size of a pencil eraser, with thousands of workers inside.

The summer shift

Wasps eat protein as larvae and sugar as adults. The workers spend the early summer hunting insects — caterpillars, flies, spiders, beetles — and bringing them back to the nest as paste-fed protein for the developing brood. This is the wasp's most useful role in any ecosystem: she is a major insect predator. Without yellowjackets and hornets, North American forests would have substantially more leaf-eating insects than they do.

In late August, when the colony stops producing brood and the workers no longer need to provide protein, their behaviour shifts. They become sugar-foragers. They start showing up at picnics, garbage bins, soft drinks, fallen fruit. This is the part of the wasp's year that most people experience as a wasp problem. The same insect that quietly hunted caterpillars in July is now competing with you for your iced tea.

Why the defence is so coordinated

If a wasp at the nest perceives a threat — a vibration in the substrate, a large moving body, a chemical alarm signal from another worker — she releases an alarm pheromone. The pheromone is a small volatile chemical that other workers smell from inside the nest. Within seconds, dozens of workers can be in the air, oriented toward the source of the alarm, ready to sting. They sting more than once because their stinger is not barbed like a honey bee's. They can sting, withdraw, and sting again.

This is why nest removal by an untrained person tends to end badly. The first disturbance triggers the alarm. The alarm triggers a mass response. The mass response targets whoever is closest to the nest. A professional response involves either treating the nest at dusk when workers are inside and less active, or applying a residual product at the entrance that workers contact as they come and go.

Where they build

In Quebec, the locations are predictable. South-facing eaves of houses, where the wood gets warm in spring and the queens land first. The void above a porch ceiling, accessed through a single small gap. The interior of a barbecue cover left out overwinter. The hollow of a deck post. The space under a shed step. Yellowjackets in particular often nest underground, using an abandoned mouse burrow or chipmunk hole as a starting point and expanding the cavity from below.

What they all share is shelter from rain, warmth from the sun, and a single small entrance that is easy to defend.

The collapse

None of this is permanent. The colony exists for a single summer. In September, the queen stops laying worker eggs and starts laying reproductive eggs — males and future queens. These mate in flight in late September or early October. The males die soon after. The mated future queens fly off and find a sheltered place to overwinter, usually under loose tree bark or inside a wall cavity. The workers in the nest, increasingly aimless without brood to feed, die over the next several weeks. By November the nest is empty. By spring, it has begun to weather and degrade. The wasps do not reuse old nests. Each spring, each surviving queen starts again from scratch.

Related reading: wasp nest removal in Montreal, South Shore wasp removal, and why MHM yards have so many in late summer.

The honest takeaway

A wasp is not malicious. She is a specialist predator and architect doing what she has done for millions of years. The conflict with humans is geometric — we have built our homes where she has built hers, and our entrances and theirs are sometimes inches apart. Treating a nest is a question of timing and chemistry. Recognizing where a nest is forming, in May or June when the queen is alone and the colony has perhaps a dozen cells, is enormously easier than addressing a four-thousand-worker yellowjacket nest in late August.