The boxelder bug, scientifically known as Boisea trivittata, is a common North American insect often recognized by its striking coloration. This true bug features a dark, black body with distinct reddish-orange markings, including three longitudinal stripes just behind its head. The adult insect is typically about a half-inch long, with an elongated, somewhat flattened oval shape.
Geographic Distribution
The boxelder bug is native to the temperate regions of North America, where it has a broad natural range. It is particularly prevalent across the United States and extends into parts of southern Canada, as well as south into Mexico and Guatemala. The insect’s distribution is closely tied to the presence of its primary food source, the boxelder tree, which is why it can be found in diverse environments from deciduous forests to urban areas. The population density of the boxelder bug often varies from year to year, depending heavily on local weather patterns. They tend to be most abundant following hot, dry summers and warm springs, conditions that favor their breeding and development.
Host Plants and Summer Environment
During spring and summer, the boxelder bug lives an active, outdoor existence centered around specific vegetation. The insect gets its common name from the boxelder tree (Acer negundo), which serves as its preferred host plant. They are also frequently found on other species of maple, such as silver maple, and occasionally on ash trees. The bugs feed by using specialized piercing-sucking mouthparts to extract fluids from the plant tissues. Nymphs and adults primarily target the developing seeds and seed pods of these trees, which are rich in nutrients. Females tend to prefer the seed-bearing (pistillate) boxelder trees for both feeding and egg-laying, often depositing their small, reddish eggs in bark crevices or on leaves. The insects spend the entire summer on the leaves, branches, and trunks of these host trees, completing one or two generations depending on the climate. While their feeding can sometimes cause minor leaf discoloration or fruit blemishes, they generally do not cause significant damage to the overall health of the tree.
Seasonal Migration and Shelter Seeking
The lifestyle of the boxelder bug changes dramatically in the fall as temperatures begin to drop and their food sources decline. Adult bugs begin a seasonal migration away from their host trees to seek out warm, sheltered locations for overwintering. Only the fully-grown adult stage of the insect is capable of surviving the cold winter months. They are strongly attracted to sun-exposed surfaces, often clustering in large numbers on the south and west sides of buildings, rocks, and tree trunks to absorb warmth. From these sunny congregation points, they begin to search for protected spaces to enter a state of dormancy. This is the phase when they become a noticeable nuisance to people. The bugs gain entry into homes and other structures through small cracks, crevices, and unsealed gaps around windows, doors, and foundations. Once inside, they hide in wall voids, attics, or crawl spaces, seeking insulation from the freezing outdoor temperatures. They remain hidden throughout the coldest months, but may emerge into living areas on unusually warm winter days, confusing the indoor warmth for the arrival of spring.