Most recently reviewed by: Pat Porter (2021)
Common Name(s): boxelder bug
Eggs are yellow when first laid, but turn red when almost ready to hatch.
Nymphs, the immature stages, of boxelder bugs are oval in shape like adults but are smaller. Nymphs are bright red and develop black markings and wings as they mature.
Adults are about 1/2 inch long and 1/3 inch wide. They are dark brownish gray to black with distinctive red to orange markings consisting of three red lines running lengthwise on the pronotum (the area behind the head). Wings are folded over the back of the body, overlapping each other. Red lines mark the lateral margins of the wings
Origin and Distribution
Found in North America, typically on boxelder trees, but also can be found on maple and ash trees as well as other plants.
Habitat & Hosts
Boxelder bugs feed primarily on the seeds of female boxelder trees. Minor hosts plants (plants from which they obtain food) include apple, ash, cherry, chinaberry, grape, peach ,plum, maple and western soapberry trees. These bugs do not damage host plants. Although they suck plant juices while feeding, they are seldom abundant enough to harm trees.
In the fall, adults and nymphs leave trees where they feed and look for sheltered areas in which to spend the winter (overwinter). Although nymphs are often present in the fall, usually only adults survive the winter.
As temperatures drop, boxelder bugs move into tree holes, cracks and crevices around foundations, and walls, and door and window casings. Sometimes the bugs move indoors. Once inside, they move to warm areas of the building and eventually move toward windows or other sunny areas. Outdoors on warm winter days, boxelder bugs move from their protected areas to sun themselves and may be seen congregating on houses or buildings. They prefer buildings with southern or western exposures.
Incomplete: egg- nymph- adult
Females deposit eggs in cracks and crevices of tree bark. After about two weeks, eggs hatch and nymphs develop into adults during the summer. There may be two or more generations per year in Texas; often several stages of nymphs and adults can be seen at the same time.
ManagementIf you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.
Inspect the outside of the structure for areas that boxelder bugs may find to be a suitable overwintering location. It is preferable to inspect and take any necessary exclusionary steps before August. Preventive actions include:
- Seal cracks and crevices and pipe/ wire penetrations with caulk or expanding foam.
- Stuff weep holes with copper mesh or plastic screening made specifically for weep holes (kits are available).
- Replace or repair any damaged window screens.
- Replace any damaged weather stripping around the doors. If you can see daylight around doors when they are closed, replace weather stripping.
- Install door sweeps on exterior doors and a rubber seal along the bottom of garage doors.
- Repair or replace damaged screens or soffit vents in the roof and eaves area of the structure.
If possible, remove host plants, such as boxelder trees. Eliminate hiding places such as piles of rocks, boards, leaves, and general debris near the house.
If you do not wish to remove the host trees, and exclusion techniques are unsuccessful, you may need to apply an insecticide. To prevent indoor migration in the fall, treat young, exposed bugs on host trees in the spring and early summer. Applications should thoroughly cover the tree trunk, limbs, and foliage.
Sprays can also be applied to hibernation areas such as the foliage and trunks of trees, building foundations, fences, sides of houses, and other outside areas where the bugs congregate. Look for active ingredients such as neem, pyrethrins, cyfluthrin, deltamethrin, and esfenvalerate. Indoors, try vacuuming up unwanted bugs.