Managing Accidental Invaders

The following Agriculture and Natural Resources article originally published in the Kentucky Pest News on November 7, 2017.

Winter is an inhospitable season for cold-blooded arthropods that survive year-round in Kentucky. Most accomplish this in an innocuous fashion–out-of-sight and out-of-mind. Unfortunately, several species of these “accidental invaders” enter structures seeking shelter from the elements. While they come from distinctly different sources, all seem to recognize their good fortune and remain indoors until lengthening daylight prompts them to leave in spring to resume their normal activities. Unwilling landlords may not see their free-loading tenants again until fall.

Household Pest Management Strategies

There is no magic solution to vanquish these interlopers. The same set of marginally effective strategies is available to those faced with these unwanted guests.


Insects moving to shelters are attracted to contrasting light and dark areas (window frames, columns, etc.) on vertical surfaces. Large numbers may accumulate on sunny south or west walls of houses and buildings where they may be sprayed directly with an appropriately labeled insecticide before they have a chance to enter.


Exclusion is the next tactic. Seal as many obvious openings as practical. In spite of the best efforts, some persistent individuals will find a way inside. For further information, refer to How To Pest-Proof/Winter-Proof Your Home (EntFact-641).

Collect & Discard

Use a vacuum to collect and discard as many invaders as possible. Once outdoor temperatures consistently remain below 50 degrees F, the influx should stop, or at least be greatly reduced. Also, these invaders do not reproduce indoors, so numbers do not increase.

Avoid Insecticides Indoors

Avoid the temptation to use insecticides indoors. “Bug foggers” or insect foggers have significant limitations and pose some significant risks. Refer to Limitations of Home Insect Foggers (“Bug Bombs”) (EntFact-643). In addition to potential exposure problems, indoor accumulations of dead insects can result in problems with carpet beetles and other scavengers.

Examples of Accidental Invaders

Below are pictured some of the accidental invaders that have been observed in Kentucky.

insect invaders

Figure 1. A brown marmorated stink bug rests on a shutter that contrasts strongly with a brick wall (Photo: Lee Townsend, UK).

Figure 2. Multicolored Asian lady beetles are especially common in areas where trees are abundant (Photo: Lee Townsend, UK).

insect invaders

Figure 3. Immature and adult boxelder bugs accumulate prior to moving to shelter. Boxelder and maples are common hosts (Photo: Lee Townsend, UK).

insect invaders

Figure 4. Face flies commonly move to shelter from nearby cattle (Photo: Lee Townsend, UK).

Figure 5. Ground beetles are common in turf and around foundations. Worn door sweeps provide a place for them to gain entry (Photo: Lee Townsend, UK)

Written by Lee Townsend, Extension Entomologist.

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