Boxelder Bugs


  • William F. Lyon:
  • Jacob G Price

Boxelder bugs feed primarily on the seed-bearing boxelder trees by sucking sap from the leaves, tender twigs and developing seeds.

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Adult boxelder bugs are flat, 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). Wings are thick and leathery at the base and membranous at the tip. There are red veins in the wings; the abdomen is bright red under the wings. The nymphs resemble the adults in shape except they are smaller, wingless and bright red. Eggs are red.

What Do They Damage?

Boxelder bugs, Leptocoris trivittatus, may become a nuisance, especially during the cool autumn months when they first cluster in large numbers on the sides of trees, houses and other structures. However, they do not damage buildings, clothing or food products, but may bite if handled carelessly. Indoors they may stain walls and curtains and produce a foul odor when crushed.

Living Habits

During the autumn months, adult and large nymph boxelder bugs congregate in large numbers, primarily on the bark of boxelder maples (Acer negundo) and then begin migrating to a place for over wintering. Only adults over winter, moving to hibernation sites either by crawling or flying.

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 appear on light painted surfaces outdoors on the south and west sides of the house, resting in the sun. Over wintering adults leave their hibernating quarters with the coming of warm weather and females begin laying eggs in crevices of tree bark and on other objects near host plants. Hatching occurs in 14 days, with nymphs appearing about the same time that new tree leaves develop. 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. Occasionally, they have been observed feeding on maple, ash, plum, cherry, apple, peach and grape, 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 pod-bearing boxelder trees. Apparently, they do little feeding damage to boxelder trees.

  • Be sure to repair and close openings where boxelder bugs can enter the house such as around doors and windows and through the foundation.
  • Eliminate potential hiding places such as piles of boards, rocks, leaves, grass and other debris close to the house.

Because these bugs breed only on female boxelder trees, removal of these trees would eliminate nuisance populations. If boxelder trees are needed for shade, ornamental beauty or other purposes, nurserymen should propagate by taking cuttings only from male trees.

Water at 165 to 180 degrees F applied directly on clusters of bugs will kill them. Avoid killing grass and other desirable plants with hot water. If hot water is not available, use a garden hose to wash away from doorways, carports and decks.

Chemical Control

Limited spraying with an aerosol pesticide labeled for crawling insects may be useful. Apply spray to outside doorsills, window ledges and doorsteps. Before using any insecticide, read the label and follow directions.

Resource(s): Insect Pests of Ornamental Plants

Center Publication Number: 34

Jacob Price
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