Have I Found a Queen Ant? An Identification Guide

Every summer, thousands of people spot a large ant walking oddly across a patio and wonder the same thing: is that a queen? In July and August in the UK, the answer is often yes. Here’s how to tell in a few seconds — and what to do next if you want to try founding a colony.

The three things to check

1. The thorax

This is the most reliable check. The thorax — the middle body section, between head and abdomen — is where the wing muscles live.

• Queen: thorax is large, deep, and boxy, clearly wider than her head. She looks front-heavy, almost hunchbacked.
• Worker: thorax is slim and low-profile, narrower than the head.
• Male: small head, small thorax, slim overall, with wings he never sheds — males look more like winged gnats than ants.

2. Wing scars

After mating, a queen tears her own wings off. That leaves small stubs or scars on the sides of her thorax — visible as little notches or bumps where wings clearly used to attach. Wing scars on a wingless ant are as close to proof as you’ll get.

3. Size and behaviour

Queens are usually — not always — noticeably bigger than workers of the same species. A Lasius niger queen is around 9mm against 3–5mm workers. Behaviour helps too: a freshly mated queen wanders alone, often in the open, searching for somewhere to dig in. Workers out in the open are usually following trails, not wandering solo.

Quick reference: common UK finds

What you found	Likely identity
Large black ant, ~9mm, wingless, alone on pavement in July–August	Lasius niger queen — the classic find
Very large dark ant, 10–12mm, hint of red, found near grassland	Formica queen (e.g. Formica fusca)
Small reddish ant, ~5–6mm, chunky thorax, late summer	Myrmica queen (e.g. Myrmica rubra)
Winged ant of any size, still flying	Wait — could be a male; check the thorax once it lands
Big-headed slim ant marching in a line	A worker; leave her to it

For photos and full care details, match your find against the species database. The nuptial flight calendar shows which species fly in which months, which narrows identification a lot.

Found one? The first hour

1. Catch her gently in any clean container — a glass and a piece of card works.
2. Set up a test tube: fill one-third with water, trap it behind a firmly pushed wad of cotton wool, add the queen, and plug the entrance loosely with more cotton.
3. Cover the tube with foil or put it in a drawer — darkness tells her she’s safely underground.
4. Leave her alone. No food if she’s fully claustral (most Lasius); a tiny drop of sugar water every few days if semi-claustral (Formica, Myrmica). Her care card tells you which.

The full setup is covered step-by-step in catching and housing a queen, and the weeks that follow in the queen care guide.

When it’s not a queen

No wing scars, slim thorax, normal size? It’s a worker — she can’t found a colony and won’t survive long alone; put her back where you found her. Winged with a tiny head? A male — he dies naturally within days of the flight either way. And if you’re unsure, photograph her next to a coin and compare against the species cards before deciding.