The Box Elder Bug (Boisea trivittata) is a common, small insect often found congregating in large numbers across North America, especially as the weather cools. Their sudden appearance near homes often leads to concern regarding potential health risks. This article examines whether they pose a threat to people, pets, or property.
The Truth About Box Elder Bug Bites
Box Elder Bugs are not considered harmful and generally do not bite humans. These insects do not bite for the purpose of feeding, nor do they possess venom or transmit diseases to humans or pets. Their mouthparts, known as a rostrum, are a piercing-sucking apparatus specialized for consuming plant fluids, not blood or human tissue.
The feeling people sometimes describe as a “bite” is typically a defensive or accidental probe. If a Box Elder Bug is trapped, startled, or lands on exposed skin, its specialized mouthpart can occasionally puncture the skin. This may result in a small, localized red mark, similar to a minor mosquito bite, but it is not a true feeding or aggressive bite. The irritation is minor and symptoms resolve quickly, usually within a few hours, without requiring medical intervention.
Identifying the Pest and Its Natural Diet
Adult Box Elder Bugs measure about a half-inch long and have flat, elongated bodies that are dark gray or black. Their most distinctive feature is the bright reddish-orange markings, which include three longitudinal stripes on the thorax and red edges on the forewings. Nymphs, or young bugs, are much smaller and appear bright red, gradually developing the dark body coloration and wing markings as they mature.
These insects are herbivores that feed primarily on certain trees, particularly those in the maple family. The scientific name reflects their strong association with the Box Elder tree (Acer negundo). They use their piercing-sucking mouthparts to extract sap from the seeds, leaves, and tender twigs of host plants. While they prefer the seeds of female Box Elder trees, they also feed on Ash and other Maples, sometimes causing minor cosmetic damage to fruits like apples and plums.
Practical Steps for Home Exclusion
Box Elder Bugs become a nuisance when they leave their host trees in the fall, seeking warm, protected sites to overwinter. They aggregate in large masses, often on the sunny, southern or western walls of homes, before entering through small openings. Once inside, they do not reproduce or cause structural damage, but their droppings can stain light-colored surfaces, and crushing them releases an unpleasant odor.
The most effective management strategy is exclusion, which involves sealing up potential entry points before the cooling weather forces them indoors. Homeowners should inspect and seal cracks, crevices, and gaps around windows, doors, and utility entry points using caulk or weatherstripping. Repairing damaged window and door screens is also a necessary step to prevent their entry.
For bugs already inside the home, the best method of removal is using a vacuum cleaner with an attachment. This allows for clean disposal without crushing the insects and releasing the foul odor.