Musings of a New Naturalist: A Tree and Its Bug
Boxelder bug adult and nymphs. Photo credit: Utah State University Extension
Our new yard is shaded by two boxelder trees (Acer negundo), thick and knobby and laden with seeds folded in fluttery winged samaras. Gradually, I’m coming to know them better by sketching and researching them. I’m grateful for their shade and refer to them as the elders.
I also began to wonder about their namesake insect, the eastern boxelder bug (Boisea trivittata). I see these conspicuous black and red bugs on the bark, leaves, patio, and lately in the house, too. One day, there were “a million” tiny red bugs under one of the trees. What were these? Baby boxelder bugs? Yup! I wondered what kind of relationship they have with the tree, and what kind of relationship we’d have with them. Would they harm the tree or us?
Fortunately, the answer is most likely that they won’t do any harm. The adults and their young, called nymphs, use their piercing, straw-like mouthparts (which place them in the order Hemiptera – true bugs) to suck sap from boxelder trees, as well as ash and maple trees, but only a massive infestation would cause defoliation. And they don’t bite! Phew!
After feeding, growing, and reproducing during spring and summer, they seek a relatively warm, sheltered place for overwintering in a state called diapause. The deep crannies in bark, especially on the south and west sides of trees, work great, as do homes.
Despite emitting a foul odor and displaying warning coloration, boxelder bugs provide food for various animals, including grasshoppers, spiders, birds, rodents, and others. They might need those “one million” nymphs I saw to keep the population going.
As the weather cools, I’ll plug up holes around our doors and wish the bugs well as they tuck themselves into bark beds of the elders.