Occasional Invaders
Boxelder Bug
Black-and-red bugs that gather by the hundreds on sunny walls in fall and try to spend the winter inside homes.
Quick facts
- Size
- 11–14 mm
- Colour
- Black with red-orange markings
- Active season
- Fall and warm spring days
- Where found
- Sunny walls, window frames, attics, near maple and boxelder trees
How to Identify
- Flat, oval black body
- Red-orange lines along the back and wing edges
- Young bugs (nymphs) are bright red
Signs to Look For
- Large clusters on south- and west-facing walls in fall
- Bugs on windows indoors on warm winter days
- Reddish stains on curtains or walls
Why It Matters
- Do not bite people or damage the building
- Droppings can stain fabrics and surfaces
- Give off an unpleasant odour when crushed
Prevention Tips
- Seal cracks around windows, doors and siding before fall
- Repair torn screens
- Vacuum bugs indoors instead of crushing them
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