Boxelder Bugs

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Although boxelder bugs (Leptocoris trivittatus) cause little or insignificant damage to boxelder trees or other host plants, they can be a nuisance pest in and around structures.

HOW DO I KNOW IF I HAVE BOXELDER BUGS?

Adult boxelder bugs are easily seen and can be found in very large numbers on the warm south and west sides of structures in early autumn.

WHAT DO BOXELDER BUGS LOOK LIKE?

  • Adults are about 1/2 inch in length, black with three red stripes on the prominent plate-like structure that covers the middle region of the body (pronotum).

  • Nymphs are red and gray. They resemble adults but do not have fully developed wings.

  • Eggs are yellow when first laid, but gradually become red as nymphs develop inside.

ARE BOXELDER BUGS DANGEROUS?

 No. Boxelder bugs are nuisance pests; however their dead bodies may attract unlikable insects that feed on them.

CAN MY HOUSE BE DAMAGED BY BOXELDER BUGS?

  • Boxelder bugs do not cause any direct damage to the structure, contents or the occupants. However, they may stain white surfaces if crushed.

  • Starting in mid‑July, boxelder bugs can be found mainly on seed-bearing boxelder trees. There is usually no noticeable injury to the trees from boxelder bugs feeding on the leaves.

WHY ARE BOXELDER BUGS IN MY HOUSE/YARD?

  • In the early spring, typically in late April to early May, boxelder bugs become noticeable to the eye again as they congregate on the sunlit sides (south/west) of the building. Then they fly off to a convenient host to lay eggs and start their lifecycle.

  • From mid-May to mid-July, adults and nymphs congregate on the low vegetation or ground near the female boxelder trees feeding on the fallen seeds produced the previous year.

  • From mid-July to mid-September, boxelder bugs congregate on the trunk of female boxelder trees and ground.

  • The migration of the second generation to the sunny sides of buildings usually begins from mid-September to mid-October. Adult boxelder bugs typically can fly several blocks, although in some rare cases they will travel as far as two miles.

  • Boxelder bugs are especially attracted to warm areas on buildings with a large southern or western exposure. Thousands of boxelder bugs can congregate on a single structure, while neighboring buildings may have relatively few.

  • Adult boxelder bugs hibernate through the winter in cracks and crevices in and around buildings.

  • On sunny and warm winter days, a few overwintering adult boxelder bugs may become active and can be seen around windows or warm places.

  • Boxelder bugs are attracted to light. Therefore, boxelder bugs may enter homes through open windows or doors, especially at night when interior lights are on. Once indoors, boxelder bugs can be seen hiding or clustering near light fixtures or around windows and vents.

WHAT DO BOXELDER BUGS EAT?

  • Boxelder bugs feed by sucking sap from the leaves, tender twigs and developing seeds.

  • Although the primary host plant of boxelder bugs is the seed-bearing boxelder tree, boxelder bugs have been occasionally observed on other plants such as, apple, ash, maple, almond, strawberry, etc. However, boxelder bugs usually cannot fully complete their life cycle on these occasional hosts.

WHAT IS THE LIFE CYCLE OF BOXELDER BUGS?

  • Boxelder boxes develop by gradual metamorphosis from egg to nymph, and then to adult.

  • In spring, female boxelder bugs lay irregular masses of eggs on leaves, in cracks and crevices of the host tree bark, or on grasses and stones near the host plant.

  • Egg masses may have from 10-25 eggs.

  • Eggs usually hatch in 11-19 days depending on temperature and relative humidity.

  • Newly hatched nymphs pass through five nymphal developmental instars. This may take up to 60 days before they become adults by mid-summer.

  • New adult boxelder bugs mate and females lay eggs to start the second generation.

  • In the fall, boxelder bugs congregate on the trunk of female boxelder trees or on the ground level by the host plants, then they migrate to the sunny sides of buildings. This is when they become most noticeably visible to people.

  • The onset of the harsh winter weather causes all immature stages of boxelder bugs to die, while adults seek overwinter shelter, which may be your house.

  • During overwintering time, boxelder bugs do not feed or reproduce.

WHAT ELSE SHOULD I KNOW ABOUT BOXELDER BUGS?

  • Studies have shown that dry and hot summers indicate a potential increase in boxelder bug numbers. This fact helps us to predict the infestation levels of boxelder bugs each year.

  • The consumption of dead insects (conspecific necrophagy) has been documented among the boxelder bugs during the hibernation. This phenomenon increases the survival rate of the overwintering adults. Whereas, cannibalism is also known among nymphs in the field.