Question: I live in Kansas City, and whenever it gets warm this winter, I have these tiny red/black bugs crawling all over my house, and they smear red when you touch them. They don”t seem to do any damage but they are starting to show up inside now. I have had them sprayed before, but they seem to keep coming back everytime it gets warm out.

ANSWER Probably what you have found are boxelder bugs. There are few other insects that have this coloration. The milkweed bug is similar, but they are found on flowers and not on trees, and they have orange markings. Boxelder bugs are red and black.

Boxelder bugs are plant feeding insects that usually utilize the seeds of boxelder or maple trees for food.

^{Box Elder Bug Illustration}

They generally prefer to be on the female (seed-bearing) trees, and are there in the spring when they leaves and seeds begin to form. Boxelder bugs have been reported on oak trees and some other tree species, and may use these trees when there are few boxelders in the area.

These insects have 2 to 3 generation per year. The fall generation overwinters in protected places.This sometimes includes sites around and in houses, which makes them a nuisance. They have some chemicals (called pheromones) that help them to gather in large numbers, so oftentimes thousands of them will gather in one place to spend the winter.

Outside: It might be best to use an insecticide that is recommended for treating the perimeter of the house and for treating ornamental plants. This way, if some of the spray contacts shrubs around the house it will not damage the leaves. Boxelder bugs can be killed with nearly any insecticide, so if you don”t get control immediately do not assume they are resistant to the chemical. They may not have been contacted because of the large number at one place, simply spray again to contact them all.

Inside: They can be removed from inside the house with a vacuum cleaner. You may have to keep doing this for several days to get them all. During the winter they can be active during warm and sunny days. They don”t bite or sting or reproduce inside of houses, but if crushed they could stain fabric.

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