The box elder bug (Boisea trivittata) is a species of true bug in the order Hemiptera, which means “half-winged.” A box elder bug undergoes a gradual metamorphosis, changing from egg to nymph and then to adult. These bugs grow to be about one-half inch (12.5 milimeters) in length. An adult box elder bug is blackish-brown with three red lines marking the thorax and wing veins. Nymphs have bright red abdomens and no wings.
Box elder bugs primarily live on female boxelder trees or maple trees, which is why they are sometimes called maple bugs. These bugs feed on a variety of soft plant tissues, such as new twigs, flowers and leaves. Their favorite food, however, is boxelder seed pods. Box elder bugs typically do very little damage to the trees they attack unless there is an exceptionally large number of bugs.
Adult box elder bugs can become household pests in the colder months when they crawl inside buildings to hibernate. They tend to overwinter in protected places such as cracks in walls, around foundations, and under windows and doors with western or southern exposures. Although box elder bugs are inactive when it is cold, heaters can wake them up and they might move into the parts of buildings where people live or work.
In warmer months, box elder bugs leave their winter locations to lay eggs on boxelder and maple trees. By late spring, groups of these bugs can be spotted sunning themselves on buildings near their feeding trees. A box elder bug has good eyesight and will generally fly away when approached by humans. During a box elder bug infestation, however, massive numbers will group together on the brick or siding of a building and not disperse when approached.
In these cases, one way to get rid of boxelder bugs is to spray them with a mixture of two tablespoons of natural soap in a gallon of water. This solution might damage vegetation and the siding of the building, however. Natural insecticides can usually eliminate the bugs with less chance of damage or staining. Both the soap mixture and the insecticide should be sprayed around any vents, doors, eaves, soffits and siding where the bugs can crawl inside of the building. The south and southwest sides of the building should receive most of the insecticide because these sunnier spots are far more likely to attract boxelder bugs.
Control is a bit more difficult once box elder bugs have invaded a building, however. Household insecticides are effective when applied directly to individual bugs, but this process can be time consuming and the chemicals in the insecticide might be toxic to human respiratory systems. The soap and water mixture mentioned above can be used inside the home, but it might stain or discolor any fabric or wood it touches. Perhaps the most effective way to keep box elder bugs out of the home is to caulk any cracks, fix broken door jams, repair torn window screens and put in new weather stripping. Removing female boxelder trees may not be the most desirable course of action, but it is certainly the most permanent solution to a box elder bug infestation.