No Harm Done: Boxelder Bugs

It’s time for fall colors. The trees are turning red, orange and yellow. And the bugs from the same color palate are looking for a warm place to spend the winter. There’s a gathering of them on the south-facing garage door just now. They’re basking in the sunshine. When it gets cold, though, they’ll head for more sheltered places to overwinter.

It’s a colorful invasion, with the brown-marbled stink bugs, the red and orange Asian lady beetles, and the black and red boxelder bugs. These latter invaders have spent the summer and fall sucking away at the leaves of the boxelder tree. The first batch of the year emerged about the first of May from last year’s hiding places. They had holed up for the winter under shingles and siding, in cement cracks and any other space they thought would protect them from the cold. It was time to mate, lay eggs and start in on the young shoots and foliage of their preferred banquet. Maple or ash will do, but the boxelder tree gets first refusal. Like the stink bugs, these are considered “true bugs” with their sucking mouth parts. The new red nymphs will hatch in a couple of weeks, grow and molt and grow again six times, ending up as adults by July. As adults they’ll have black or dark gray wings with red edgings and three red lines on their backs. Their abdomens are also red. their legs and antennae are black.

The red is supposed to remind birds and rodents and other predators that they taste nasty, but they get eaten anyway. Birds seem to heed that warning although chickens will eat them. The bugs are oval-shaped, and about half an inch long. Like their cousins the stink bugs, they put off a rather nasty odor if you smash them. They don’t contribute song to the soundscape. Instead, they contribute to the scent-scape by communicating with pheromones. They leave trails of scent to mark their passing or to invite their brethren in for tea.

A couple weeks after their last molt, they mate and lay eggs on mostly female boxelder trees. These eggs produce the next generation of the summer. This last generation will mature by the end of September and this is the generation that is trying to find their way into my house for the winter. Hopefully the house is tight enough to keep most of them out. In some years there are major invasions and they have to be dealt with by vacuuming them up. This year doesn’t seem too bad though.

The boxelder bug gets its name from the boxelder tree that it favors. On Owl Acres, the woods are full of boxelders so there’s plenty of habitat for them here. They don’t really hurt anything. The trees are not damaged by their nibbling and sucking on leaves and seeds. In the house they don’t bite either. They do smell bad if smashed and can leave excrement stains on the walls.

We’ll leave them to their plans but keep them out of the house.

Photo from Wikimedia.org by Rbreidbrown. Alt text: Boxelder bug reaches the end of the line, courtesy of a giant, hairy, black-eyed beast.  The robber fly scores a tasty, fragrant dinner.