Boxelder Bugs
(Boisea trivittata)
Black-and-red bugs that swarm on sunny walls in fall before entering homes to overwinter.
Overview
Boxelder bugs are common fall invaders in Bowling Green. They are closely associated with boxelder trees (a type of maple) and feed on the seeds, leaves, and flowers of these trees during warmer months. In autumn, they congregate in large numbers on the south and west sides of buildings, seeking warmth before entering structures to overwinter. While they do not bite, sting, or cause structural damage, their large numbers and tendency to stain surfaces with excrement make them a significant nuisance pest.
Appearance
Boxelder bugs are about 1/2 inch long with a flat, elongated oval body. They are primarily black with distinctive red or reddish-orange markings along the edges of the wings, on the thorax, and on the abdomen. Nymphs are smaller and predominantly bright red. Their flat profile allows them to squeeze into very tight spaces.
Habitat
During spring and summer, boxelder bugs are found on and around boxelder, maple, and ash trees. In fall, they aggregate by the hundreds or thousands on warm, sun-facing exterior walls of buildings. They enter through cracks, gaps, and openings to overwinter in wall voids, attics, and behind siding. They emerge on warm days during winter and fully exit in spring.
Diet
Boxelder bugs feed primarily on the seeds of boxelder trees, but they also feed on maple and ash seeds. They use piercing-sucking mouthparts to extract plant juices. They do not eat anything indoors and do not damage home furnishings or structures.
Lifecycle
Adults overwinter in structures and emerge in spring to feed and mate on host trees. Females lay clusters of reddish eggs on tree bark, leaves, and seeds. Nymphs hatch in about 2 weeks and develop through five stages. One to two generations are produced per year. Adults begin congregating on buildings in late September and October.
Signs of Infestation
- !Large aggregations of black-and-red bugs on sunny exterior walls, especially in fall
- !Bugs entering through window gaps, door frames, and utility openings
- !Dead or sluggish bugs found around windows and light fixtures indoors during winter
- !Reddish-brown staining on walls, curtains, or fabrics from excrement
Prevention Tips
- ✓Seal cracks and gaps around windows, doors, siding, and foundation
- ✓Repair or install screens on windows, vents, and weep holes
- ✓Remove female (seed-bearing) boxelder trees from the property if practical
- ✓Apply exterior perimeter treatments in early fall before aggregation begins
Professional Treatment
Exterior perimeter treatments applied in early to mid-September are the most effective strategy. Once bugs have entered wall voids, vacuuming live individuals is the best interior option. Avoid crushing them indoors as they can stain surfaces. Long-term, reducing or removing boxelder trees nearby and thorough sealing of entry points are the most sustainable solutions.
Did You Know?
- •Boxelder bugs are true bugs (order Hemiptera) with piercing-sucking mouthparts.
- •They produce a foul-tasting compound that deters predators.
- •A single south-facing wall can attract thousands of aggregating bugs in fall.
- •They rarely bite, but when they do (usually while being handled), the bite is harmless.
About 1/2 inch
Black with red or orange markings
6
Elongated oval, flat
Box elder bug, Maple bug
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Other Occasional Invaders in Our Library
Brown Marmorated Stink Bug
Shield-shaped invasive insects that enter homes in large numbers in fall and release a foul odor when disturbed.
Cluster Flies
Large, sluggish flies that enter attics and wall voids in fall to hibernate in large clusters.
Earwigs
Distinctive insects with rear pincers that hide in moist areas and enter homes during wet weather.
Millipedes
Slow-moving, many-legged arthropods that invade homes in large numbers after heavy rains.