The boxelder bug, Boisea trivittatus, is familiar to most people, though they may not be able to identify it by name. The adults are about a 1/2-inch long and have backs that are black with orange or red stripes beginning behind the head. The wings lay flat over the body in an overlapping manner that forms an X shape. The young bugs (nymphs) are less familiar; they are only about 1/16 inch long and are bright red when they hatch.
Though their sheer numbers can be off-putting to many people, these are not insects that pose any danger whatsoever to people or animals—even the feeding they do on plants is not likely to cause serious damage. But these flying bugs with red stripes can appear in very large numbers and can be very annoying. And they may stain walls, furniture, and drapes with feces spots that are unpleasant, though not much of a health hazard.
The Biology and Lifecycle of the Boxelder Bug
During the warm days of spring and summer, boxelder bugs live and breed in boxelder, silver maple, and ash trees. Although they feed on the leaves, flowers, and seed pods of the trees, they do not cause much notable damage, so people rarely pay much attention to them during these months.
But in the fall, when the boxelder bugs begin to take shelter in the structure of homes, the problems begin. Boxelder bugs often gather on the sun-warmed exterior walls, then squeeze into tiny cracks beneath siding, and under eaves. Usually, the insects simply overwinter there until the warmth brings them out again in the spring.
However, these bugs are attracted to warmth, and this means that they may be drawn out of hiding by the heated air inside your home. This typically happens because the indoor warmth fools them into believing that spring has arrived. As is the case with other insects such as stink bugs and squash bugs, boxelder bugs can detect temperature differences of as little as one degree.
8 Ways to Keep Boxelder Bugs Out of Your Home
Vacuum Up the Bugs
Use a shop vacuum cleaner with a long hose attachment to gather up the live boxelder bugs from the exterior surfaces of your home as they congregate. Often, it will be the west and south sides of your home where the bugs are most present, since these get the most warmth from the sun. Make sure to empty the vacuum cleaner bag into the outdoor trash immediately. The more outdoor bugs you remove, the fewer will enter the walls and make their way indoors.
Vacuuming is also effective in winter for gathering up any bugs that have found a way into your home.
Clean Up Landscaping
Remove piles of rocks, leaves and other debris around your home. These areas provide the ideal hiding places for boxelder bugs, as well as warm surfaces that attract them. Keep the area around foundations free of leaves and weeds. Removing long grasses will discourage boxelder bugs.
Spray Exterior With Water
Dislodge bugs from siding with a forceful spray of water. Boxelder bugs are easily drowned. Washed off the outside of your home, they won't be able to get into the home through cracks and crevices.
A solution of two-parts water/one-part dish soap can be sprayed on the exterior of the home to kill bugs in the fall. However, this has to be sprayed directly on the bugs—it does not have a residual effect for bugs landing on it. A soapy solution can also work to kill bugs that do make it indoors. The dead bugs can then be swept or vacuumed up.
Boiling water poured over groups of boxelder bugs will kill them; remember, though, that this will also kill plants and grass.
Seals Cracks and Crevices
Caulk all cracks, crevices, gaps, and openings in your home's structure. The tiniest cracks are enough to allow boxelder bugs to enter your walls in their effort to escape the cold.
Although exclusion techniques won't always completely eliminate the boxelder bugs' entry, they can reduce the number of entry points and the number of bugs that get in. This is most effective when combined with other techniques.
Never squash a boxelder bug with a flyswatter, as it can leave a stain on surfaces. Vacuuming is a much more effective way to eliminate a boxelder bug that has made it indoors.
Install and Repair Insect Screens and Weatherstripping
Repair any torn or broken door or window screens; boxelder bugs can fit through the smallest tear in a window screen. Windows missing their screens should be fitted with new ones. Also make sure weatherstripping around windows and doors and below the garage door is in good condition.
Although it sounds extreme, the most permanent control of boxelder bugs is the removal of any boxelder or silver maple trees near the home because these are the principle sources of food and breeding habitat. Boxelder, silver maples, and most ashes are not particularly valuable landscape trees, so removal may even improve the look of your yard.
Spray Exterior Walls With Residual Insecticide
Call a pest management professional to spray a residual insecticide on the exterior walls of the home where the bugs are found. This will help prevent the bugs from landing for a while, but be aware that it will not remain effective once cold weather sets in. Toxic chemical sprays should be a last resort, and it's worth considering whether eliminating a harmless insect is really worth the environmental risk.
Residual pesticides are typically applied by professionals since homeowners may not be allowed to purchase or handle them.
Spray Trees for Nymphs
A professional can also use a power sprayer on the trees to kill the boxelder nymphs before they can grow into adults and move into your home. Be aware, though, that such pesticides will kill all insects, including beneficial pollinators. The use of toxic chemicals is questionable when it comes to controlling a harmless insect.
What Causes Boxelder Bugs in the House?
Boxelder bugs enter your home for one reason—in search of warmth in which to spend the cold months of winter.
As their name implies, boxelder bugs are attracted to boxelder trees, as well as silver maple trees. If you have either of these trees around your home or in your neighborhood, it's likely that you'll spot boxelder bugs at some point. As soon as the cooler weather hits in the fall, boxelder bugs begin to seek shelter for the winter and are often attracted to the warm, sunny sides of homes. From there, they slip into cracks and gaps in the siding or around doors and windows and can end up seeking shelter inside the home during the winter.
How to Prevent Boxelder Bugs in the House
In summary, preventing boxelder bugs from reaching the interior of your home is accomplished by eliminating breeding and feeding areas, getting rid of hiding spots around the exterior of your home, sealing cracks and crevices that allow them entry into your walls, or by killing the bugs before they can get in—or with a combination of these strategies.
Boxelder Bugs vs. Stink Bugs
The boxelder bug (Boisea trivittatus) is sometimes confused with the stink bug (various species in the Pentatomidae family of insects). Certain species of stinkbug do bear a strong resemblance to B. trivittatus. In fact, boxelder bugs, too, release a strong unpleasant scent when threatened, as a homeowner may realize if they ever catch them by hand.
Boxelder bugs are clearly identified by the red-orange veining and marking on the wings and abdomen, while only a few species of stinkbug show such markings. And boxelder bugs are the species that routinely seeks entry into the warmth of homes; stinkbugs don't exhibit this behavior.
How Do I Identify a Boxelder Bug?
At about a 1/2-inch long, boxelder bugs (Boisea trivittata) have narrow black bodies with red edge lines on their trunk and red lines on the edges of their wings. These markings make it appear as though its wings form an upside-down V when they are lying flat. They are avid flyers and can often travel for several miles at a time.
Do Boxelder Bugs Carry Diseases?
Boxelder bugs are not known to carry or spread any diseases that affect humans, animals, or plants.
Do Boxelder Bugs Do Any Damage?
Boxelder bugs can do some damage to fruit and leaves in the fall, but this is minor and the insect is not considered an agricultural pest. Even its feeding on the plant parts of its favorite trees—boxelders, some maples, and ashes—does not seriously harm the trees. As far as humans are concerned, this is one of the most harmless insects around. In rare cases, large numbers of boxelder bugs may do minor damage to houseplants.
How Long Do Boxelder Bugs Live?
These insects live about a year. The eggs typically hatch in the spring, and the adults mature to overwinter in a warm spot, then lay eggs and die the following spring. They do not lay eggs indoors, but rather return to the trees in order to reproduce.
Do Boxelder Bugs Bite?
These insects are non-aggressive and rarely bite humans or animals. Their piercing-sucking mouthparts are capable of puncturing skin and produce a reaction similar to a mosquito bite.
Boxelder Bugs. National Pesticide Information Center, Oregon State University, U.S. Environmental Protection Agency, 2020.
Smitley, David et al. How to Control Invasive Pests while Protecting Pollinators and Other Beneficial Insects. Michigan State University Invasive Species, 2019.