Jeffrey Hahn, Asst. Extension Entomologist
People have recently been experiencing problems with boxelder bugs in their homes, sometimes in large numbers. Despite the circumstantial evidence, these insects are not reproducing indoors; all of the boxelder bugs you see now entered homes last fall. When they get into wall voids, attics, and similar places, they often cluster in large groups. As the outdoor temperatures warm up (or sometimes as people turn their heat up), the outer layer of these insects will receive the most warmth and become active. They will then move to the inside of buildings where it is warm. Eventually another layer of insects becomes active and so on. This is why boxelder bugs and other dormant insects do not all emerge at the same time.
Unfortunately, there are not many good options for dealing with boxelder bugs and other overwintering insects at this time of year. There is nothing practical for treating them while they are dormant in hidden areas and preventing their emergence. And once they are in your home, they only real option is to physically remove them, e.g. with a vacuum cleaner.
The best time to deal with boxelder bugs and other insects that seek harborage for the winter is in late summer or fall before they start to move to buildings seeking overwintering sites. The best methods for reducing these insects are by sealing up cracks and spaces that may allow them entrance into your home combined with a timely treatment of an appropriate residual insecticide. Some insects will still get inside but you should be able to reduce the number that would otherwise get inside. Keep in mind that boxelder bug populations vary from year to year and in 2012 many people experience an above average number of them. If you traditionally do not see many, you may see populations return to normal in 2013.
Click here for more information on boxelder bugs.