Box elder bugs are a common sight around homes, particularly during certain times of the year. These insects are primarily known as nuisance pests due to their tendency to congregate in and around residential structures. While their presence can be bothersome, understanding their habits and characteristics helps in managing them effectively.
Identifying Box Elder Bugs and Their Diet
Box elder bugs (Boisea trivittata) are identifiable by their distinct appearance. Adults are approximately 1/2 inch long with brownish-black bodies and prominent red or orange markings. They feature three longitudinal red stripes on their thorax and red margins on the basal half of their wings, which often overlap to form an “X” shape on their back. Young box elder bugs, called nymphs, are smaller and appear bright red, gradually darkening as they mature with black wing pads and legs.
These insects are primarily herbivores, feeding mainly on sap and seeds from specific trees. Box elder trees are their preferred food source, from which they extract fluids from developing seeds, leaves, and tender twigs. They also feed on other maple and ash trees, and occasionally on fruits like apples, cherries, plums, grapes, and strawberries. Box elder bugs use piercing-sucking mouthparts, a specialized proboscis, to draw sugary fluids from plant tissues.
Seasonal Movements and Habitat
Box elder bugs exhibit seasonal movements linked to their life cycle. They emerge from hibernation in the spring as temperatures rise, seeking host trees to feed and reproduce. During summer, they primarily reside on box elder, maple, and ash trees, where females lay red eggs in bark crevices or on leaves. Nymphs hatch from these eggs and feed on the host trees, developing into adults.
As autumn approaches and temperatures drop, adult box elder bugs change their behavior. They aggregate in large numbers on warm surfaces like rocks, tree trunks, and the sunny sides of buildings, seeking overwintering sites. They then migrate towards homes, looking for sheltered spots to hibernate, often entering through cracks and crevices in walls, attics, or basements. This movement indoors is driven by their need for warmth and protection from the cold.
Impacts on Plants and Homes
While box elder bugs feed on plants, they do not cause significant damage to mature trees. Their feeding may result in minor discoloration of foliage or some superficial damage to fruits, such as slight puckering. However, the overall health of established trees is not severely impacted, and they are not considered a serious agricultural pest. Young seedlings or particularly stressed plants might show more noticeable signs of feeding.
When box elder bugs enter homes, they are primarily considered a nuisance pest. They do not bite or sting humans, nor do they transmit diseases. These insects do not cause structural damage to homes, nor do they reproduce indoors. Their main impact as indoor pests stems from their tendency to gather in large numbers, stain surfaces with reddish-orange fecal droppings if crushed, and release an unpleasant odor when handled roughly or squashed.