Ladybirds in the house: why do they gather in autumn, and what to do?

A cluster of ladybirds in a window frame, by a door gap or in the attic usually appears in autumn: the beetles are looking for a sheltered place to spend the winter. This is a seasonal event, not a danger.

Ladybirds do not breed in the house and do not damage wood, food or clothing. The real nuisance is their numbers, yellow stains and an unpleasant smell. Do not crush them: collect them with a vacuum cleaner, then find and seal the gaps they get in through.

The ladybird best known for overwintering inside buildings in large numbers is the harlequin ladybird (Harmonia axyridis), a species introduced to Georgia. If the insect is flat and brown rather than round, it may be a stink bug: see stink bugs in the house.

In autumn, harlequin ladybirds leave their summer feeding sites and look for winter shelter, and a building is one such place.

According to University of Kentucky entomologists, flights are heaviest on sunny afternoons when it warms up after cooler weather. The beetles favour the sunny southwest side of a house. Contrasting light and dark features attract them more than the colour or material of the house, and homes shaded from the afternoon sun are less likely to be infested.

Once on a building, they crawl into cracks around window and door frames, behind fascia boards and siding, and into attics and wall voids. Poorly maintained buildings with many openings are the most vulnerable.

The table lists the most common situations. Each one is explained in more detail below.

The harlequin ladybird (Harmonia axyridis) is native to East Asia and was introduced to Georgia. According to the RHS, it is 8–10 mm long and very variable in colour and markings.

The most useful feature is the pale, whitish area behind the head (the pronotum). University of Kentucky entomologists describe a small dark mark shaped like an M or W on it in most harlequin ladybirds. The wing cases range from tan to red, and the number of spots varies.

Do not rely on a single feature: colour and spot count do not identify a ladybird. The RHS warns that the harlequin ladybird is easily confused with some native species.

It can be. According to the RHS, the two common forms of the harlequin ladybird are black with two red spots and orange with many black spots.

A black beetle with red spots can also be a different species, so colour alone is not enough. For a reliable identification, take a close photo from above that shows the head and the area behind it.

The seven-spot ladybird (Coccinella septempunctata) is, according to the RHS, almost always red with seven black spots.

The harlequin ladybird is far more variable: orange or red with many spots, or black with red spots. If a ladybird has more or fewer than seven spots, or a black back, check the area behind the head for the pale colour and the M or W mark.

The ladybird known for overwintering in buildings in large groups is the harlequin ladybird, so a cluster on your window may not be a native ladybird at all. You can only be sure after a close look.

Usually not. According to University of Kentucky entomologists, a ladybird that lands on skin may bite or pinch; it feels like a pinprick and is seldom serious. The beetles do not attack wood, food or clothing.

In some people, large numbers of beetles can cause allergies, ranging from eye irritation to asthma. After handling the beetles, do not touch your eyes before washing your hands. If you notice an allergic reaction, see a doctor; if you have trouble breathing, call 112.

When disturbed, a ladybird releases a yellowish defensive fluid from its leg joints. It has an acrid, unpleasant smell and stains surfaces.

So do not crush the beetles or sweep them off light-coloured fabric or walls with a broom: University of Kentucky entomologists note that a broom is more likely to cause staining. A vacuum cleaner is better.

No. Ladybirds do not reproduce indoors. The beetles seen in spring are usually the same ones that came in the previous autumn.

In late winter or early spring, as it warms up, they become active again, first on the sunny side of the house. Some wander indoors while trying to get outside, which is why they are often seen near windows and lights.

Ladybirds that got indoors are easiest and safest to remove mechanically, without chemicals. The RHS considers it neither desirable nor necessary to control this beetle, which feeds largely on aphids; it is enough to remove it from living rooms.

1. Use a vacuum cleaner. University of Kentucky entomologists call it the easiest way to remove them.
2. If you want to release the beetles, put a handkerchief between the hose and the collection bag so they stay in it.
3. Release the collected beetles outdoors, away from the house.
4. Pick up a single beetle carefully with a piece of paper or a jar, without crushing it.
5. If ladybirds keep appearing in the same place, there is a gap there that needs sealing.

The longest-lasting solution is sealing the entry points. University of Kentucky entomologists recommend doing it in late spring or summer, before the beetles start looking for shelter in autumn.

• Windows and doors: seal cracks around the frames with caulk or sealant.
• Eaves, siding and utility lines: seal cracks around fascia boards, siding, and where pipes and cables enter the wall.
• Larger holes: plug them with cement, expanding foam or copper mesh.
• Screens: repair window and door screens, and fit screening behind attic vents.
• Doors: fit a tight door sweep or threshold. A gap of about 3 mm is enough for a ladybird to get in.
• If very many beetles get in every autumn, ask a professional about an outdoor treatment: according to University of Kentucky entomologists, it must be done in autumn before the mass entry and does not work in late winter.

Some quick fixes do not solve the problem or create a new one.

• Do not crush ladybirds: the fluid leaves a smell and a stain.
• Do not use aerosols or foggers indoors: according to University of Kentucky entomologists, they are often ineffective and can stain surfaces.
• Do not spray insecticide into wall voids: killing beetles hidden there is seldom effective.
• Do not touch your eyes after handling the beetles.