Boxelder bugs look a bit like stretched-out stink bugs but without the pungent odor. They belong to a group called the scentless plant bugs. The adult bugs are about half an inch long, mostly black in color and accented with red edges. The immatures, or nymphs, look like miniature versions of the adults but are bright red in color with developing wing buds instead of full-blown wings. While their bright colors might seem to draw the attention of predators such as birds, they have little fear from being eaten. Although they are scentless, they release a chemical which makes them extremely distasteful. Birds quickly learn to avoid these bugs.
Boxelder bugs get their name from a plant they feed on, the boxelder tree, but they’ll happily settle for maple or ash. While they sometimes feed directly on leaves with their straw-like mouthparts, they prefer to suck out the contents of the winged seeds (those neat little seed pods that helicopter when you throw them in the air). These bugs cause very little damage to plants and are not considered a major agricultural pest. They are, however, a pest of homeowners because of their presence.
Before winter arrived, you may have noticed clusters of boxelder bugs hanging out on the south side of trees, rocks, or houses. By now, they’ve settled into a hibernative state called overwintering and won’t be showing themselves until around March or April. You probably won’t notice them by the time it warms up, because they’ll be focused on feeding and reproducing on their host trees. You’ll notice them again in the fall when the temperatures begin to drop. They’ll congregate in sunny areas near their host plants where they annoy homeowners with their presence and droppings. After congregating, the bugs migrate together to find suitable overwintering locations. Wood piles, leaf litter, overgrown shrubbery, and human structures are all attractive places to spend the winter.
If boxelder bugs have made their way into your house, you’ll need to determine how they are getting in and fix the issue. Otherwise, expect to see these bugs, as well as other overwintering insects like ladybugs, invading your home every year. If vast numbers of these bugs are in your home, use a vacuum to collect them without crushing them. The vacuum bag can be frozen to kill the bugs and then discarded. Bagless vacuums can be emptied into a trash bag. I recommend emptying your vacuum contents into a bag outside, then tying the bag and tossing it into your outdoor trash receptacle. While most modern vacuum cleaners are powerful enough to pummel the bugs, it is always wise to empty out the contents sooner rather than later. If any bugs are still alive, they could crawl out and continue to bother you. A single bug can be gently picked up in a paper towel. Avoid smashing them, as their fluids can stain surfaces. They do not reproduce indoors, rather, they aim to spend the winter months in your home, but your home is too warm. Instead of going into dormancy, they wander around thinking that its time to wake up.
Boxelder bug populations are at their highest when the summer is hot and dry. Although they cause no harm to people or plants, some people dread the arrival of these bugs every year. If you can’t tolerate them, you could go to the extreme and cut down your boxelder, maple, and ash trees. However, be aware that there may be neighboring trees that are not on your property. If your home is sealed up tight, the bugs will eventually move on to find overwintering sites and you won’t see them again until next year.