Fall Household Pests Back »

Written collaboratively by Amanda Bachmann and Adam J. Varenhorst.

The recent climate update predicts that the majority of South Dakota is still a few weeks away from the first hard frost of the season. While this is good news for crops and gardens, it does mean a longer season for insect and other arthropod activity.

For insects and arthropods that are showing up inside, the best course of action is to determine their point of entry and close it. Check around windows and doors for gaps, and inspect any cracks or crevices in walls and foundations. In most cases, an insecticide is not necessary for the fall invaders and they can be managed with a vacuum, empty jar, shoe, or a broom.


Fig 1. Cluster fly. Photo by Mohammed El Damir, Pest Management, Bugwood.org

Fig 2. Picture winged fly. Photo by Whitney Cranshaw, Bugwood.org

This is the time of year when cluster flies and picture winged flies start moving into structures. Cluster flies will survive the winter indoors, and are often noticed on mild winter days. They do not reproduce indoors. Picture winged flies also move indoors, but they don’t survive the winter. House flies are also active and ending up inside. They reproduce on decaying organic matter, so it is possible to have a breeding population inside that is active all winter. Sanitation (taking out trash regularly, cleaning drains, etc.) is the best way to handle small populations.

Boxelder Bugs

Fig 3. Boxelder bug adult. Photo by Joseph Berger, Bugwood.org

This is another example of an insect with adults that spend the winter indoors. Boxelder bugs are harmless, and should just be swept up or vacuumed. Their activity increases during warm days in the fall, and also during the winter when they will congregate near sunny windows.

Multicolored Asian Lady Beetle

Fig 4. Multicolored Asian lady beetles. Photo by Bruce Watt, University of Maine, Bugwood.org

This is one of our introduced lady beetle (aka ladybug) species and it will congregate in structures as the weather cools. The multicolored Asian lady beetle activity generally increases in the fall as crops are being harvested and they are seeking shelter for overwintering. Activity of this lady beetle increases on warm fall days, and they will congregate on structures. They are often active through the entire winter, with increased activity on warm days. Multicolored Asian lady beetles emit a pungent odor when disturbed, and are best removed using an empty jar with an available lid. There are reports that when canister vacuums are used to remove this pest the odor persists in the canister for extended periods of time.


Mosquitoes will remain active until the first frost. It is important to continue to wear protective clothing and personal repellents when engaged in outdoor activities, as it is still possible to get West Nile Virus in the fall.

Have a Pest Question?

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 (605.773.8120).


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