Pest guide
Asian Lady Beetles
Asian lady beetles look almost identical to native ladybugs but behave very differently. In fall they swarm warm, south-facing walls and squeeze indoors to overwinter — sometimes in the thousands. They bite mildly, leave orange staining, and emit a defensive odor when threatened.
01 — Identification
What asian lady beetles look like
Size
1/4" long, oval and domed.
Color
Orange to red with 0–19 black spots; pale 'M' or 'W' shape behind the head.
Shape
Rounded dome, short legs and antennae.
How to tell them apart
- The dark 'M' marking on the white pronotum is the easiest tell.
- Native ladybugs lack the M and don't cluster indoors.
02 — Life cycle
How they grow and reproduce
One to two generations per year. Eggs to adult in about a month.
- 1
Egg
3–5 days
Yellow clusters on the underside of leaves.
- 2
Larva
12–14 days
Spiny black-and-orange grubs that feed on aphids.
- 3
Pupa
5–6 days
Attached to a leaf, immobile.
- 4
Adult
2–3 years
Overwinters in groups in protected spots.
03 — Risks & behavior
What to watch for
Health risks
- They can bite or pinch, though not seriously.
- Defensive secretions (yellow 'reflex blood') stain walls and trigger allergies in some people.
Home & property risks
- Mass clusters in attics, wall voids, and window frames.
- Persistent odor when crushed.
Behavior at a glance
Diet
Adults and larvae are voracious aphid predators — beneficial in the garden.
When active
Day-active; clusters on sunny walls in early fall before entering structures.
Peak season
Most problematic September through October during the indoor migration.
- Originally released in the U.S. for biocontrol; now widespread.
- Light-colored homes attract larger clusters.
04 — Treatment
How to get rid of asian lady beetles
Seal entry points first, then treat exterior walls before the fall migration.
- 1
Inspect siding, soffits, attic vents, and window frames for gaps.
- 2
Caulk and screen openings in late August.
- 3
Apply a peppermint-based exterior spray to sunny walls in early September.
- 4
Vacuum any indoor clusters (don't crush — they'll stain).
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05 — Prevention
Keep them from coming back
- Seal attic vents with fine mesh.
- Caulk siding gaps and replace torn screens before October.
- Vacuum clusters rather than squashing them.
- Repeat exterior treatment after heavy rain.
06 — FAQs
Frequently asked questions
Are Asian lady beetles the same as ladybugs?+
They're closely related but distinct. Asian lady beetles cluster indoors and can bite or stain; native ladybugs do neither.
Why are they in my house in winter?+
They seek warm, dry spots to overwinter. Once inside wall voids and attics they stay dormant until spring warmth wakes them.
Should I kill them?+
They're beneficial outdoors, so relocate or vacuum when possible. Reserve sprays for entry points and exterior walls.
