Its a few days past Halloween, but talking to people about box elder bugs (Boisea trivattatus) reminds me of a horror movie. When the weather starts cooling down in the fall, peoples homes are sometimes inundated with masses of red and black bugs that freak out many homeowners, especially since it seems you get rid of one batch and another group follows. Kind of like buggy zombies.

Thankfully, box elder bugs are fairly innocuous except for making a mess on and in homes with their excrement. They dont bite, and are just looking for a warm, dry place to hunker down for the winter. But they do poo as the travel, and if there are enough of them, its best to clean up the areas where theyve congregated.

Lifecycle

Their lifecycle is fairly simple. The adults that plaster themselves all over the exterior walls of houses usually find nooks and crannies in which to hide until warm weather coaxes them out of their winter beds. In the spring, they prefer to gather and feed on the female (seed bearing) box elder trees. Theyre rarely found on the male trees, but will sometimes go to maple or ash trees if box elders are scarce.

In the late spring to early summer, the female box elder bugs lay eggs in the cracks and crevices in the trunk and branches of the box elder tree. In a few days, the nymphs emerge, and have a ready source of food. Depending on the length of the season, these young of the year can lay eggs themselves rearing a second generation in one season.

Harmless Box Elder Bug

Box elder bugs really dont do any harm in the garden, and theyre really not often seen during the summer. Its usually only when the weather starts to change in the fall that theyre noticed. It typically starts with a few bugs loitering on the southern or western sides of the house, where its the warmest, but some years there seems to be a living mat of red and black, particularly when it was a warm spring followed by a hot, dry summer.

The box elder bugs are looking for a chink in the house armor making another good reason to seal up the house for the winter. The best way to keep them out is to carefully inspect any places 1/8 inch or larger where they can squeeze through. Caulk around windows, utility outlets and spigots to prevent them from overwintering in the walls.

Some homes, particularly those with vinyl siding, are open invitations to box elder bugs since its practically impossible to seal up the spaces in the siding. Fortunately, most newer homes have a house wrap underneath the siding that will prevent them for finding their way inside, although some people still dont want to provide a free shelter under the siding. The easiest way to catch them is to vacuum them with a Shop-Vac, or blast them with the hose. Itll take several days, if not weeks, because they keep coming back, but its ultimately effective.