Pest Control
When is a cockroach not a cockroach? When it's a cockchafer
A big brown beetle crashing into the window on a May evening. It is almost certainly a cockchafer: harmless, native and nothing like a cockroach.
Every spring we take calls from people who think a cockroach has flown into the house. It is almost always a cockchafer, also called the May bug: a big, noisy, completely harmless native beetle that is drawn to lit windows on warm evenings.
The short version
- Cockchafers are large brown beetles that fly at dusk in May and June and are attracted to light.
- They do not bite or sting, they do not infest homes and they need no treatment.
- The quickest way to tell one from a cockroach is the antennae.
What is a cockchafer?
There are two cockchafers in Britain. The common cockchafer (Melolontha melolontha) is the one found across much of England, including the Midlands. The forest cockchafer (Melolontha hippocastani) is less common and more local, mostly in wooded areas.
Both go by plenty of country names, including May bug, Billy Witch and doodlebug. They are big, at around 2 to 3cm long, with chestnut-brown wing cases, a dark head and thorax, a row of white triangular marks along each side and a pointed tail. In flight they are slow, clumsy and loud.
The life cycle of the cockchafer
Adults emerge from the soil in late April and May and live for around five to seven weeks, feeding on the leaves of trees such as oak. Females lay their eggs in the ground, and the larvae, large white C-shaped grubs, live underground for three to four years feeding on plant roots before pupating and emerging as adults.
Because of that long life underground, cockchafers can be much more noticeable in some years than others.
Identifying a cockchafer
The name May bug comes from when they appear: late spring and early summer, usually flying at dusk. Most people meet one when it bumps against a lit window or flies in through an open one.
The antennae are the giveaway. A cockchafer's are short and end in a fan of leaf-like plates, which the beetle can spread open. Males have seven of these plates on each antenna and females six, so the males' fans look larger.
Cockroach or cockchafer?
The two are easy to tell apart once you know what to look for:
- Antennae. A cockroach has very long, thin, whip-like antennae, often as long as its body. A cockchafer has short antennae ending in a fan.
- Shape. A cockroach is flat and oval, built for squeezing into gaps. A cockchafer is chunky and rounded, with hard wing cases.
- Behaviour. Cockroaches avoid light, run fast and hide around kitchens, appliances and boiler cupboards, mostly at night. Cockchafers fly towards light, buzz loudly and blunder about.
- Timing. Cockchafers turn up in spring, one or two at a time. Cockroaches appear at any time of year and in increasing numbers.
Are cockchafers harmful like cockroaches?
No. Cockroaches are a hygiene risk because they move between drains, waste and food areas and can contaminate surfaces with bacteria. If you think you have them, see our cockroach control page.
The cockchafer is harmless. The pointed tip of the female's abdomen looks like a sting but is used to push eggs into the soil. The larvae can damage lawns and crop roots in large numbers, which is a matter for gardeners and farmers, but the beetles pose no risk to people, pets or buildings.
What to do if one gets in
Turn off the lights near it, open the window and let it find its own way out, or move it outside with a glass and a piece of card. Drawing the curtains on warm May evenings stops most of them coming in at all. No treatment is needed or appropriate.
If you are not sure whether you have found a cockchafer or a cockroach, send us a photo and we will tell you.
More pest guides
Ground beetles: what's crawling into your home?
A black beetle on the kitchen floor in the morning is almost always a ground beetle that wandered in overnight. Harmless, and usually fixed with a draught strip.
Read the guide →Trouble in the eaves: dealing with starlings nesting in your home
Starlings return to the same gap in the eaves year after year. The law protects an active nest, so timing matters: wait for the young to leave, then close the gap.
Read the guide →Not sure what you're looking at?
Send us a photo or describe it. We will tell you what it is, whether it needs treating at all, and what it would cost, before anyone comes out.