Bugs That Come In From The Cold
Cluster Flies
Fall arrives. You open the windows to let the fresh air into your previously closed home, and alas, upon lifting the window, you find what appears to be several hundred "dead" flies. But wait, a few of them are beginning to move. They are not dead! You slam the window, hoping none escape into your home!
What
are these flies and why are there so many?
And why do they appear to be coming to life?
What you see are known as Cluster flies and they become pests of homes, schools, hospitals, and commercial buildings throughout much of the United States. Cluster fly larvae parasitize a common species of earthworms, Allolobophore rosea, during the summer. Near fall, the summer populations of adults emerge from the soil and look for a nice, warm place to hibernate, i.e., your attic or window sills. These crafty little insects will travel over a mile for a suitable hibernation site.
Cluster flies overwinter and emerge from hibernation in the spring to breed and lay eggs on the soil surface near the earthworms that the young infest. Hibernation habits of Cluster flies are the most troublesome because of their sheer numbers. Stimulated by warm weather, they begin to become active again in early spring and seek openings to return to the outside.
Ladybugs
About the time of the first frost, Ladybugs may also come into your home through any crack, crevice, open window, or hole. They just want to hibernate until Spring and do not cause any big problem except for their presence. They will become active when it gets warm again and try to find their way back outside, where they continue their very helpful work of eating lots of other insects, especially several kinds of major plant pests. They may also become active during any unusually warm periods during the Winter. They will often fly to windows or lights. Some kinds of Ladybugs, such as the Asian Ladybug, can come into a house literally by the thousands. That can be very disturbing to people living in the house. The best thing to do when they become active in the Spring is to help them get outside again, alive.
Bugs
Several plant-feeding true bugs, in the insect Order Hemiptera, sometimes come into houses in large numbers. These include the Box Elder Bug, the Western Conifer Seed Bug, and several different "stink bugs." Infestations of these bugs are a direct result of their building up a large population on their host plants near the home they came into. Some of them will fly to outside lights at night, then come in unnoticed when a door of window is opened the next morning. Most of these are large enough to be noticed soon after they come inside.
The best control measure for each of these overwintering pests is exclusion, by sealing up all cracks or other entry points, and possibly by applying a residual chemical barrier to deny access to exterior cracks or holes which cannot be effectively closed.
You can sweep or vacuum these pests from the window or attic and dispose of them. If you use a vacuum, remember to remove the bag when you are finished, seal it in a plastic bag, and dispose of it with your normal trash or garbage.