The insect commonly known as the Box Elder Bug (Boisea trivittata) is a member of the “true bug” order, Hemiptera. These insects do not possess biting mouthparts for defense or aggression against humans or pets. While they can sometimes cause a minor skin puncture, they are not considered biting insects like mosquitoes or ticks. They are not harmful and pose no threat of disease transmission to people.
Identifying the Box Elder Bug
The adult Box Elder Bug is easily recognized by its distinctive coloration and size, typically reaching about one-half inch in length. Its body is primarily black or dark brownish-black, contrasted by striking red or reddish-orange markings. Specifically, adults feature three prominent red longitudinal stripes on the thorax, the area just behind the head. The wings also have fine red margins and a diagonal red marking that overlaps when the insect is at rest.
Immature Box Elder Bugs, called nymphs, are smaller and appear bright red with black markings that become more pronounced as they grow. They are commonly found feeding on the female box elder tree, which is their preferred host, though they also feed on maple and ash trees. Identifying these insects is often possible by observing their host trees or noticing their habit of congregating in sunny areas.
Understanding the Bite Risk
Box Elder Bugs are equipped with specialized mouthparts called a proboscis, which is a tube-like structure designed for piercing and sucking plant sap. This feeding apparatus is adapted for extracting fluid from leaves and seeds, not for biting flesh or drawing blood. They do not have mandibles for chewing or tearing, meaning they cannot bite defensively like a wasp or spider.
The rare instances of a skin puncture occur when an insect is severely provoked, crushed against the skin, or mistakenly probes for moisture. Because they are not blood feeders, this action is accidental and not an attack. The resulting sensation is generally described as a quick, mild pinprick. The puncture is not venomous, and the insect does not transmit any human diseases.
Any reaction to this accidental piercing is usually minimal, manifesting as a small, temporary red mark or minor local irritation. The discomfort typically resolves quickly without the need for medical intervention. Since their mouthparts are not designed to penetrate deeply, the risk of secondary infection is exceptionally low with standard hygiene practices.
Preventing Nuisance Aggregation
Box Elder Bugs become a nuisance when they gather in large numbers, a behavior known as aggregation, especially in the fall. They are seeking warm, sheltered spots to spend the winter, often congregating on the sunny, south-facing sides of buildings. As temperatures drop, they seek entry points to overwinter inside wall voids, attics, and other protected areas.
To prevent their entry, homeowners should focus on exclusion methods before the cold weather arrives. A thorough inspection of the building exterior is necessary to seal small cracks and crevices in the foundation, window frames, and door casings. Applying caulk or weatherstripping to these gaps can significantly reduce access.
Repairing or replacing damaged window and door screens is another effective measure to block entry. Indoors, the safest and most recommended method for removing any bugs that have found their way inside is using a vacuum cleaner. This avoids crushing them, which causes them to release a foul-smelling compound and can leave stains on surfaces.