Throughout March, people have been having problems with nuisance insects in their homes, especially cluster flies, boxelder bugs, and multicolored Asian lady beetles. Fortunately, these insects are harmless, although they can be annoying, especially when a large number of them are present. Here are a few things to keep in mind when dealing with these insects.
First, it is important to know that these insects are not reproducing indoors. Because they emerge from their hiding places periodically throughout the winter and early spring, it appears they are laying eggs and their offspring are emerging. In fact, all of the insects you see now entered your home last fall. They hibernate in balls or clusters in wall voids, attics, and similar areas. As the temperatures warm, the insects in the outer layers become active first and then emerge into the living quarters of the home, explaining why they do not all become active at the same time.
Because these insects are emerging from hidden sites, it is not practical to treat them to prevent their emergence. Once they are out in the open, your best bet in dealing with them is physical removal, such as vacuuming. Eventually, all of these overwintering insects will become active and move away from their overwintering sites. And fortunately, for those trapped in homes, they are short lived.
To minimize these kinds of problems in the future, it is important to treat these insects in the fall as they are first trying to enter your home. This is a two pronged approach. First it is important to inspect the outside of the home during summer and seal spaces and gaps that may be used by these insects to get inside. This should be followed up with an insecticide application in the fall, just as these insects are trying to get inside. This insecticide application is typically applied to the outer perimeter of the home. It is not possible to prevent all nuisance insects from entering into a home, but you can reduce the number that do causing fewer problems later during the winter and spring.
You can find more information on cluster flies, boxelder bugs and lady beetles at the University of Minnesota Extension website: http://www.extension.umn.edu or information specific to multicolored Asian lady beetles at: http://www.extension.umn.edu/distribution/housingandclothing/M1176.html