Insect · Low risk
Asian Lady Beetle
Every fall, the Asian lady beetle gathers by the thousands on sunlit walls, then slips into attics and window frames. Harmless to the structure, it stains surfaces and gives off a sharp odour.
5-8 mm · Orange with a black “M”
§1Distinctive features
How to identify it
The most reliable marker is the black “M” drawn on the white pronotum, just behind the head. The number of spots ranges from 0 to 20, most often 19, and the colour goes from pale yellow to red, with black forms bearing red spots, whereas Quebec’s native lady beetles vary little in colour from one individual to the next.
§2Habitat
Where to find it
It gathers on south- and west-facing walls warmed by the sun, then gets in through foundation cracks, torn window screens and roof vents. Indoors, you will find it in the attic, in light fixtures and around windows.
§3Reproduction
Lifecycle
It does not breed indoors: the lady beetles you see in winter are the ones that came in during the fall. As long as the entry points stay open, the same building gets recolonized every year.
§4What to look out for
Signs of infestation
- Clusters of orange insects on sunlit exterior walls
- Dead lady beetles piling up on window sills
- Smelly yellow stains on curtains, walls and ceilings
- Sudden reappearance indoors during winter thaws
§5Why act fast
Risks
- Foul-smelling yellow secretion that stains fabrics and light surfaces
- Allergic reactions and irritation in sensitive people
- Possible light nip, harmless but surprising
§6Prevention
How to avoid it
- Seal cracks, window frames and foundation joints before September
- Install screens in good condition on vents and soffits
- Vacuum the insects rather than crushing them, to avoid stains
- Have the exterior perimeter treated in late September, just before they gather
§7Pro method
How MW works
Inspection
Inspection of the south and west walls, foundation, soffits and attic to locate entry points and clusters already settled in.
Preparation
Sealing of cracks, repair of window screens and installation of mesh on vents to physically block access.
Treatment
Application of an approved residual barrier on the exterior perimeter and around frames, before the fall migration.
Follow-up
Vacuuming of insects already inside, cleaning of stains and a spring follow-up to confirm the treatment worked.
§8Your questions answered
Frequently asked questions
Is the Asian lady beetle dangerous for my house?
Why do lady beetles come into my home in the fall?
How do I get rid of Asian lady beetles?
The Asian lady beetle follows the crops and orchards where it hunts aphids: fall clusters are first and foremost a problem in farming areas. Our technicians seal and treat the perimeter around Saint-Hyacinthe, in the Haut-Richelieu, in Granby and in Sherbrooke, as part of our pest control service.
Sources used for this fact sheet: Espace pour la vie, Montréal Insectarium · Natural Resources Canada · MAPAQ, Asian lady beetle leaflet · IRIIS phytoprotection.
React quickly, sleep well.
The longer the infestation lasts, the more expensive it becomes.