This week I received a somewhat anxious phone call regarding legions of black bugs with red racing stripes amassing on the sunny side of my friend’s home. Always eager to witness insect invasions, I dashed over and was delighted to see a vanguard of boxelder bugs planning their attack. Why do these strange bugs lay siege to some homes, but not others? As with most questions regarding real estate the answer is location, location, location. The landscape surrounding my unfortunate friends provides just the right habitat to support a thriving population of boxelder bugs. Several mature red and silver maples grace the landscape. In a nearby swale boxelder, also a species of maple and ash trees abound. These trees produce seeds used by the boxelder bugs as food.
In addition to seeds of maple and ash, favored cuisine of these bugs include the sap and seeds of plum, cherry, and many other trees, shrubs, and vines. Plans for the impending invasion were laid months ago by boxelder bugs that survived the ravages of last winter. With the return of warm weather in spring, bugs moved from hibernal refuges into the greening landscape. After consuming fallen seeds and plant sap for several days, female boxelder bugs lay eggs on the bark and leaves of trees, or on the ground. Each female can lay 200 to 300 eggs that hatch in a few weeks. Tiny red nymphs with black legs consume a liquid diet of plant nutrients during the growing season. As the nymphs mature, black wing pads grow longer and finally cover the abdomen as they molt to adulthood. Depending on geographic location boxelder bugs can complete one to three generations each year.
During late spring and early summer, they move to boxelder and other seed-bearing trees. The largest populations of bugs accumulate on female trees that produce seeds. In autumn, usually in October and November in central Maryland, red nymphs and black adults collect en masse on trunks of boxelders. In the wild, adults fly and walk to rock formations, fallen leaves, or crevices in trees to gain protection from the wicked winter. In cities, suburbs, and the country, our homes provide refuge. Swarms of bugs become a nuisance on sunny porches, siding, and around windows and doors as bugs seek overwintering locations. They gain entry into homes through cracks in the foundation, gaps in siding around windows and vents, and beneath doors if sweeps are in poor repair or missing. On cold wintry days bugs are inactive, but when temperatures warm, they sometimes roll out and wander around your home.
Managing boxelder bugs
Boxelder bugs are not harmful to humans or pets. They do not bite, sting, or reproduce indoors. However, squashing them on drapes or walls will produce a nasty stain. To limit the number of boxelder bugs taking up residence in your home, eliminate hiding places such as piles of lumber, rocks, leaves, and branches close to the house. Weatherproof your home to help bug-proof it. Caulk and seal vents and openings where electrical and plumbing utilities enter and exit the house. Repair or replace door sweeps and seal any openings around windows, doors, and foundation. If all of this fails, other cures are at hand. One unfortunate homeowner called me each November to discuss the annual invasion and vent frustrations over boxelder bugs. After dutifully suggesting my standard remedies for half a decade, I was elated to receive my annual phone call and learn that boxelder bugs were no longer an issue for my entomophobic friend. They sold their home and moved to less buggy lands. Learn more about home invaders by visiting previous episodes of Bug of the Week - Home Invaders I, Home Invaders II, and Home Invaders III. If you see a black bug with red shoulders that doesn’t quite look right like boxelder bug attempting to storm your barricades, check out Bug of the Week Rain tree surprise - Golden rain tree bug.
We thank Jeff and Linda for sharing their boxelder bugs and inspiring this Bug of the Week. The wonderful reference “Urban Insects and Arachnids: A Handbook of Urban Entomology” by William Robinson was used as a reference.
To learn more about boxelder bugs, visit the following web sites: