Box elder bugs generally do not bite humans or pets, and they are not considered harmful. These insects are primarily a nuisance, especially when they gather in large numbers.
Understanding Box Elder Bugs
Box elder bugs (Boisea trivittata) are identifiable by their flat, elongated oval bodies, typically about half an inch long. They are predominantly black with distinct reddish-orange markings, including three stripes behind their head and red edges on their wings, which overlap to form an ‘X’ shape on their backs. Young box elder bugs, known as nymphs, are smaller, about one-sixteenth of an inch, and bright red, gradually darkening as they mature.
These insects are native to the western United States but can be found across North America wherever box elder trees are present. They primarily inhabit box elder trees, and occasionally maple and ash trees, feeding on their sap, leaves, and seeds using piercing-sucking mouthparts. While they can feed on the fruits of plum, apple, and other trees, they do not cause significant damage to the plants themselves.
In the fall, as temperatures drop, box elder bugs aggregate in warm, sunny spots, often on the exterior of buildings, before seeking sheltered places to overwinter within cracks and crevices in homes. This behavior is driven by their need to find warmth and shelter for the colder months.
Do Box Elder Bugs Bite?
Box elder bugs are not known to bite defensively or for feeding purposes like mosquitoes or ticks. Their mouthparts, known as a proboscis, are designed for piercing plant tissues to extract sap, not for biting humans or animals.
While rare reports suggest they can accidentally prick human skin, such as when landing on a person, any resulting irritation is usually minor, presenting as localized redness, swelling, or mild itching, and typically resolves quickly without medical treatment.
Box elder bugs do not transmit diseases to humans or pets. They are considered nuisance pests because of their tendency to invade homes in large numbers, and when crushed, they can release an unpleasant odor and potentially stain surfaces with their bodily fluids or excrement.
Managing Box Elder Bugs
Managing box elder bugs primarily involves preventing their entry into homes, as they are largely a nuisance pest. During late summer and early fall, seal potential entry points around a home before they seek overwintering sites. This includes repairing or replacing damaged window and door screens, sealing cracks and crevices in foundations and exterior walls, and ensuring proper sealing around utility pipes, vents, and other openings.
For bugs that have already entered a home, physical removal is the most practical and recommended method. Vacuuming or sweeping them up is effective, and it is important to dispose of them outdoors or seal the vacuum bag to prevent them from returning.
Chemical treatments are generally not necessary due to their harmless nature and limited effectiveness once the bugs are indoors. They do not reproduce inside homes and typically only survive for a few days indoors, although large numbers may emerge on warm winter days. Maintaining a clean yard by removing debris, leaf litter, and keeping organic materials away from the foundation can also help reduce their presence near the home.