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Boxelder Bugs

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A Nuisance Pest                                                              

Boisea trivittata, commonly known as the boxelder bug or maple bug, is a familiar insect to the residents of Medicine Hat. They often become an issue in the fall when they try to move into homes to overwinter and again in the spring when they emerge as the weather starts to warm up. Anytime we have a warm winter, there’s a good chance that boxelder bug populations will explode.

Boxelder bugs are typically black with red or orange markings. Adults are about 12.7 millimeters (0.5 in) in length. Immature nymphs are bright red when they first hatch and love to congregate for warmth. Boxelder bugs release a pungent compound which deters predators and allows them to accumulate without being preyed on.

Their favorite food is the seed pods from the female boxelder tree (aka Manitoba maple). They are rarely seen on male boxelder trees. They have also been known to feed on ash trees and other maple species. Boxelder bugs do very little damage to the trees they encounter.

Fortunately they do not bite and are essentially harmless to property, structures, pets and house plants (even in large numbers). They tend to become a nuisance when they congregate along the warm outside walls of houses and buildings, along foundations, under loose siding, under windows and in cracks in walls and doors. This creates even more of a problem when they find their way into homes and buildings. Their excrement can stain curtains, furniture and clothing and they emit a foul odor when crushed.


In the spring adult boxelder bugs emerge from their overwintering sites. We tend to see them in huge swarms along buildings, fences, and at the base of trees and foundations. They are getting ready to fly to the nearest boxelder tree and deposit their eggs. The eggs are oval shaped and rust colored. They hatch into young nymphs within a few days and go through a series of molts before becoming an adult.

They tend to live quietly among the trees during the summer months but become a nuisance again in the fall as they begin their search for a protected place to overwinter. They are naturally attracted to the south and west exposures of buildings where they gain entry through any openings.

 Prevention & Control

Removal of the female boxelder tree is typically not recommended since the bugs are also attracted to ash and other maple species. When possible, only male boxelder trees should be planted.

Here are some tips for managing these pests:
• Seal cracks in foundations, windows, doors and other entry points. Reattach any loose siding.
• A solution of liquid laundry detergent and water can provide safe and effective control when applied directly to the bugs.
• Vacuum or sweep up boxelder bugs in your home.


Identifying colors: Black, Grey, Red, Orange