Fall invaders
From about late August into November, insects that spend summer outdoors move into houses to wait out the cold. They don't breed inside or hurt the house, but they can show up by the hundreds.
The fall invaders
12 kinds, most dangerous first. Tap one for photos, the danger rating and what to do.
Asian lady beetleBe careful
Hobo spiderBe careful
Barn funnel weaverHarmless
Boxelder bugHarmless
Brown marmorated stink bugHarmless
Camel crickets (native)Harmless
Cluster flyHarmless
Giant house spiderHarmless
Greenhouse millipedeHarmless
House cricketHarmless
Pill bugHarmless
Western conifer seed bugHarmlessWhy they move in
Asian lady beetles, brown marmorated stink bugs, boxelder bugs, western conifer seed bugs and cluster flies all spend the winter as adults in a sheltered spot. Outdoors that might be under bark or in rock crevices. A house does the job better, especially the sunny south and west walls, which warm up in the afternoon and draw them in.
Most of them get into wall voids and attics, not the living space. On warm winter days, and again in early spring, some wander toward the light and end up inside rooms, which is why people often notice them in February or March.
Keeping them out
- Seal gaps before they arrive. Late summer, by the end of August, is the time to caulk around windows, siding, fascia boards and pipes.
- Repair screens, including attic and soffit vents.
- Vacuum the ones that get inside and empty the bag outdoors. Crushing stink bugs and lady beetles releases a smell, and lady beetles can stain.
- Skip sprays inside wall voids. Dead insects in the walls can draw carpet beetles that feed on them.
- Be patient in spring. Most leave on their own as the weather warms.
Other fall arrivals
Crickets, camel crickets, pill bugs and millipedes move toward foundations as soil cools and may come in under doors. Male giant house spiders and hobo spiders wander in late summer and fall looking for mates, so more spiders on the floor in September doesn't mean an infestation.