Indoor Arthropods Looking for a Way Out Back »

An orange, multicolored asian lady beetle.

Written collaboratively by Amanda Bachmann and Adam Varenhorst.

Recent warm weather in February and March hastened the spring activity of adult insects that overwinter in human-occupied structures. Many of these insects entered homes and garages in the fall and are now looking to move outdoors to continue their lifecycle.


Cluster flies and picture winged flies that moved in during the fall are making their reappearance indoors. Cluster flies generally survive the winter months indoors, and are now becoming more active and congregating near sunny windows. They do not reproduce while inside. Picture winged flies also moved indoors, but they don’t survive the winter and thus are being found dead near windows.

Boxelder Bugs

This is another insect where the adults moved inside during the fall months. Boxelder bugs are harmless, and should just be swept up or vacuumed when found (Figure 1). They congregate near sunny windows and their activity is increasing along with the temperatures.

Figure 1. Boxelder bug.

Western Conifer Seed Bug

The Western conifer seed bug mostly escaped notice this past fall. They overwinter as adults in sheltered locations, but they do not congregate in large numbers like some of the other insects mentioned. Adult bugs are now becoming active and looking for an escape to the outdoors so they can mate and lay eggs for the next generation (Figure 2). They are not feeding or reproducing indoors, and they are not considered to be a major pest once outside.

Figure 2. Adult Western conifer seed bug.

Multicolored Asian Lady Beetle

This is an introduced lady beetle (aka ladybug) species that also overwinters indoors and is now being found (both alive and dead) around sunny windows and other exits. Because there can be extensive color variation as well as markings these adult beetles are best identified by the “W” or “M” present on the white segment directly behind the head (Figure 3).

Figure 3. Adult multicolored Asian lady beetle.

Pest Management

To prevent these insects (or, more accurately, their offspring) from re-entering homes in the fall, the best course of action is to determine their point of entry and fix it. Check around windows and doors, and inspect any cracks or crevices in walls and foundations. In most cases, an insecticide is not necessary and the insects can be managed with a vacuum or a broom.

If you have an insect indoors and would like help identifying it, please submit a clear picture to the Plant Diagnostic Clinic or contact Amanda Bachmann.


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