Boxelder bugs often invade buildings, especially during the warm days of autumn, to seek sheltered sites for overwintering. They are attracted to lights and will readily fly in open doors and windows. Indoors, these bugs create a nuisance by their presence, produce a foul odor when crushed, and may stain curtains with fecal matter. Outdoors, they can be found in large numbers on the sides of trees, buildings and other structures. Large populations are often correlated with long, hot, dry summers. During warm winter and spring days, they may become active, moving from their hiding places into living spaces. Although they do not cause damage to buildings, clothing, food or humans, boxelder populations can be a nuisance.

Description:

Adult boxelder bugs are flat-backed, elongate, narrow, about 1/2 inch long, 1/3 inch wide and dark brownish-black with three lengthwise red stripes on the pronotum (area behind the head). The head is black with the "beak" or proboscis reddish-orange and the long, thin, four-segmented antennae are half as long as the body. Wings are thick and leathery at the base and membranous at the tip. There are red veins in the wings and the abdomen is bright red under the wings. The nymphs, or immatures, resemble the adults in shape except they are smaller, more rounded, wingless and bright red. Eggs are dark reddish-brown.

Life Cycle:

During the autumn months (around October 1), adult and large nymph boxelder bugs congregate in large numbers, primarily on the bark of boxelder trees (see diagram below), and then begin migrating to a place conducive to overwintering. Only full-grown adults overwinter, moving to hibernation sites either by crawling or flying. They may crawl from a nearby tree or fly as many as two miles to find shelter. These bugs hide in cracks and crevices in walls, in door and window casings, around foundations, in stone piles, in tree holes and in other protected places. On warm days during winter and early spring, they sometimes reappear on light-painted surfaces outdoors on the south and west sides of the house, resting in the sun. Overwintering adults leave their hibernating quarters with the coming of warm weather (last week of March), and females begin laying eggs (late April to early May) in crevices of tree bark, stones, leaves, grasses and on other objects near host plants. Eggs hatch in 11 to 19 days, with bright-red nymphs appearing about the same time new tree leaves develop. There are five nymphal instars. The instars become progressively darker red with each stage. In July, new adults lay eggs that result in a second generation by early autumn. Boxelder bugs feed primarily on the seed-bearing boxelder trees by sucking sap from the leaves, tender twigs and developing seeds. They have occasionally been observed feeding on ash, maple, plum, cherry, apple, peach, grape and strawberries, causing some scarring or dimpling of fruits. However, boxelder bugs seldom develop in large enough numbers to become a nuisance, unless able to feed on seed-bearing boxelder trees. Apparently, they do little actual feeding damage to boxelder trees. There may be one to two generations per year.

Control:

Cultural:
Since boxelder bugs feed and reproduce primarily on pistillate (female) boxelder trees, removal of these trees, especially around the house, would eliminate nuisance populations. Some towns have outlawed pistillate trees. However, adults are capable of flying two or more miles for suitable hibernation quarters. If boxelder trees are desirable for shade, ornamental beauty or other purposes, use only propagation (cuttings) from the staminate (male) trees. Eliminate potential hiding places such as piles of boards, rocks, leaves, grass and other debris close to the house. Rake leaves and grass away from the foundation in a six- to ten-foot-wide strip, especially on the south and west sides of the structure. Be sure to caulk and close openings where boxelder bugs can enter the house, such as around light fixtures, doors and windows, unscreened vents, holes in walls and foundations, around utility pipes or conduits, air conditioners, etc. They are also attracted to lights and can fly in open doors or windows. Screen all windows, doors, crawl spaces, exhaust and roof vents and louvers. Clusters of bugs may be killed by pouring boiling water on them. Be careful to avoid killing grass and other desirable plants with boiling water.

Insecticides:
Should boxelder tree removal be impractical, treat the young, exposed boxelder bug nymphs on the trees during spring and early summer to prevent potential large populations and indoor migrations in the autumn. Insecticidal soap can be used to kill congregrated boxelder bugs. Treating boxelder tree trunks with residual insecticides can kill migrating insects.

Adapted from the Ohio State University Extension, 1999. Photo
from the Kansas Cooperative Extension.