Pest Profile: Boxelder Bugs

Boxelder bugs (scientific name Boisea trivattata) are named after one of their primary homes, the boxelder tree. They are known to occasionally enter structures during the winter to stay out of the harsh cold. Although a nuisance pest, they are actually native to the United States. They are specifically found in the western and eastern United States as well as eastern Canada. The females will lay their eggs on stones, eaves, grass, shrubs, and trees, and the eggs will hatch two weeks later. Although there are two generations of these insects a year, they are not often seen until the fall when temperatures start to drop. In the fall they congregate in large numbers on the south sides of trees, buildings, and rocks where the sun hits. In the adult stage, boxelder bugs are black with reddish-orange markings on their backs. During their immature stages, they are mostly red with black legs.

While boxelder bugs don’t transmit disease or cause any significant structural damage, that doesn’t mean they are welcome house guests. During the winter they will enter homes and structures to overwinter, hiding within voids. Thankfully, boxelder bugs have piercing-sucking mouthparts that don’t allow them to bite. However, they do produce a secretion that can leave a red stain on fabric furniture and drapes. Boxelder bugs can also leave a foul odor when they are crushed. This nose-wrinkling secretion helps them stay safe: its foul taste protects them from natural enemies. Even though these pests mean no physical harm to humans, they can create unwanted scents and stains.

Another natural protective measure of boxelder bugs is their bright red coloration. This is what scientists call aposematism. Aposematism refers to the appearance of an animal that warns predators it is toxic, distasteful, or dangerous. One way that an animal will advertise this warning is through color. The bright red coloration of boxelder bugs is their own way of saying, “STOP! I am dangerous and will give you indigestion!” Although they aren’t tasty, they sure will leave a bad aftertaste. So how do you “respect your boxelders” and prevent these unwanted insects from entering? Be sure to weatherproof all of your home’s doors and windows to eliminate any openings through which they could enter. This will help keep boxelder bugs where they belong – outside of your home – all year round.

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