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Asian lady beetles gathering on sunny house walls in fall

September to October

Multicolored Asian lady beetles, an orange beetle native to Asia, swarm onto sun-warmed exterior walls each fall while hunting for cracks to spend the winter in. They favor the south- and west-facing sides of light-colored houses, the spots the sun heats the most.

Why this time of year

Nights are turning cold in eastern Massachusetts while afternoons can still turn warm and sunny, and that exact combination, a cold night followed by a warm sunny day, is what sends these beetles out looking for a wall to gather on and a crack to overwinter in.

How to notice it

  1. Pick a warm, sunny afternoon that comes right after a cold night, that mix of conditions is what triggers the gathering.
  2. Walk to the side of your house that catches the most afternoon sun, usually the south- or west-facing wall.
  3. Look over light-colored siding, window and door frames, and soffits for clusters of small orange-and-black beetles rather than single insects.
  4. Check again on the next warm, sunny afternoon after a cold night; flights run into late October.

Try this with kids: Can you find the warmest, sunniest wall of our house? Count how many ladybug-looking beetles are resting there right now.

overwinter: survive the cold months in a sheltered spot instead of staying active

Sources

  • extension.psu.eduOverwintering aggregation begins around the start of October, is triggered by a sunny warm afternoon following a cold night, and the beetles are attracted to sunlight reflecting off south- or southwest-facing walls.
  • yardandgarden.extension.iastate.eduLight-colored buildings and walls in full sun attract the most beetles; flight to buildings runs mid-September through October. (Page dated 2016 and carries a 'may not be the most current' disclaimer.)
  • extension.umn.eduBeetles fly to buildings between late September and late October when temperatures are above 65F before freezing sets in, and are most numerous on the south and west sides of buildings. (URL now redirects under .../yard-and-garden-insects/, same content.)
  • homegarden.cahnr.uconn.eduConfirms the same fall behavior, gathering in large groups on the sunny side of buildings before entering through cracks, reported by a Northeast/New England extension office.

Checked against these sources on September 22, 2026.

In the guide for September, October

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