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How to identify it
- Adults are about 1/2 inch long and dark brown to black, with red eyes, three red lines on the plate behind the head (one down the middle and one along each side), narrow red edges on the wings and a red abdomen.[2][6][5]
- Wings lie flat on the back at rest.[2]
- Young nymphs are bright red and wingless; as they grow they develop dark wing pads.[2][5][6]
- Eggs are straw-yellow when laid and turn red as the nymph develops. The Forest Service describes them as rusty red and about 0.06 inch (1.5 mm) long, laid in small clusters on leaves or in rows in bark crevices.[3][5][6]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Milkweed bugs | Similar colors, but mostly orange-red with large black patches or bands rather than mostly black with thin red stripes.[1] |
| Western boxelder bug | A western species (Boisea rubrolineata) with the same habits and three red lines on the pronotum, the species covered in UC IPM's Pest Notes. The Forest Service says it ranges from British Columbia south to California and east to Nevada, Utah and Texas, and its orange-red bands are slightly narrower and paler.[2][6] |
| Red-shouldered bug (golden raintree bug) | Feeds on golden raintree seeds and can also invade homes. The three lengthwise red lines on the boxelder bug's pronotum separate it from this and other look-alike true bugs.[6][2] |
Where it lives
Found wherever boxelder trees grow, especially female seed-bearing trees; the eastern boxelder bug ranges through much of the eastern United States. Sources differ on where adults spend the winter: UC IPM lists cracks in walls, door and window casings, building foundations and the inside of houses, while Kentucky says they typically overwinter in leaf litter and only occasionally get into homes or businesses.[1][2]
Biology and life cycle
Overwintered adults leave their shelters in spring as boxelder buds open and fly back to host trees, where females lay eggs on leaves, stones and in bark crevices.[3][4][6]
Most areas have two generations a year, the second usually larger than the first; cooler areas with short growing seasons may have only one, and Penn State says one to two in Pennsylvania.[6][2][3]
Nymphs and adults feed mostly on boxelder seeds, and also on leaves, flowers and tender twigs. They sometimes feed on maples, ash and fruit trees such as apple, pear and plum.[1][3][5][6]
In fall they gather on the warm south and west sides of tree trunks, rocks and buildings, then move under rocks, steps and decking or into buildings for the winter. Only adults survive the winter.[6][3][5]
On warm, sunny days in winter and early spring, overwintering adults become active and may rest on sunlit south- and west-facing walls.[2][6]
Winged adults can fly several blocks, so they may come from a neighbor's tree.[2]
Damage and signs
Health risk
Boxelder bugs don't sting, and Kentucky says there is no evidence they transmit disease. Kentucky says they don't bite; Colorado State says bites on people have been reported on rare occasions, and Clemson says they occasionally bite when handled.[1][4][5]
Control
Prevention
Clear leaves, weeds and debris from a 6- to 10-foot strip around the foundation, especially on south and west sides, and sweep up fallen boxelder seeds, which feed adults as they emerge in spring.[2][6]
Removing female boxelder trees near the house is the most lasting fix, though bugs can still fly in from a neighbor's tree. If you plant boxelder, the Forest Service suggests a seedless cultivar.[6][4][2]
Keep them out
Before fall, repair torn screens and seal cracks around doors, windows, vents, light fixtures, pipes and air conditioners with caulk or weatherstripping. Screen crawl space and attic vents; Clemson suggests at least 16-mesh screen.[2][6][5]
Traps and physical control
Vacuum or hand-collect bugs that get inside, and repeat as needed during the fall migration.[2][3][1]
Outdoors, spray clusters with soapy water. The Forest Service gives 5 tablespoons of liquid detergent or 1/2 cup of dry laundry detergent per gallon of water; it kills only the bugs it hits and can damage leaves.[6][4]
Pesticides
Insecticides are rarely needed. The Forest Service says boxelder bugs have developed resistance to many commercially available insecticides, and UC IPM advises against using sprays for them inside the house.[6][2]
Why boxelder bugs gather on your house
As fall approaches, boxelder bugs gather in large numbers on the sunny south sides of trees, buildings and rocks, then crawl into cracks looking for a protected place to spend the winter.[3][6]
They overwinter as adults in walls, around doors, windows and foundations, especially on south and west sides, and come out on warm fall, winter and early spring days.[4]
They seldom reach nuisance numbers unless a female boxelder tree, whose seed pods are their favorite food, grows nearby.[4][6]
They head back to host trees in late April or early May as the buds open, so indoor problems should be over by late May.[3][4]
Getting rid of boxelder bugs inside
Vacuum up live and dead bugs; it's the simplest indoor control.[3][4][6]
Find where they come in, usually cracks under or behind baseboards, around window and door trim and around exhaust fans or lights in ceilings, and seal those gaps with caulk.[3]
Don't dust wall voids or attics with insecticide: carpet beetles can feed on the dead bugs and then move on to woolens and stored foods.[3]
Foggers and crack-and-crevice sprays kill the bugs you can see but don't stop more from emerging, so they aren't a long-term fix.[3]
Indoors they don't reproduce, and while they may probe house plants, they don't damage them.[4]
Outside: sealing, soapy water and trees
Sealing is the best way to keep them out: caulk cracks around windows, doors, siding, utility pipes, chimneys and fascia with good silicone or silicone-latex caulk, and repair screens.[3]
Laundry detergent and water sprayed directly on clusters is cheap, safe and effective, though it only kills bugs it hits and can damage plants.[4][6]
A hard spray from a hose washes clusters off walls. Clemson says water between 165 and 180 °F kills them; keep it off grass and plants and take care not to burn yourself.[5][2]
Exterior insecticides break down in sunlight within days to a week, and most labeled for building exteriors aren't very effective against boxelder bugs.[3][4]
Where sealing isn't possible, a licensed pest control operator can apply a pyrethroid perimeter treatment in fall, just before the bugs gather.[3]
The most permanent fix is removing female, seed-bearing boxelder trees near the home, though that may not be practical. The Forest Service notes some municipalities prohibit planting female boxelder trees for this reason.[4][3][6]
Where sources disagree
Biting: Kentucky says boxelder bugs don't bite; Colorado State says bites on people have been reported on rare occasions; Clemson says they occasionally bite when handled.[1][4][5]
Egg hatch: UC IPM says nymphs hatch in a few days; Penn State and the Forest Service give 10 to 14 days, Clemson about 2 weeks and Kentucky 11 to 19 days.[2][3][6][5][1]
Winter shelter: Kentucky says they typically overwinter in leaf litter and only occasionally get into homes; UC IPM, Colorado State and the Forest Service list buildings and houses among their usual overwintering sites.[1][2][4][6]
Vacuums: Penn State and Colorado State recommend vacuuming bugs indoors; Clemson suggests a shop vacuum instead of a household vacuum, because the odor is hard to get out of the hose.[3][4][5]
Range: Kentucky says the species occurs through much of the eastern United States and Penn State says east to west as far as Nevada; the Forest Service describes it throughout the East and adjoining Canada west through the Great Plains, plus riparian areas of the central and southern Rockies, the Colorado Plateau and California's Central Valley.[1][3][6]
Common questions
- Will boxelder bugs breed in my house?
- No. They need boxelder trees to reproduce; bugs trapped indoors eventually die.[2][1]
- Do boxelder bugs bite?
- They don't sting, and Kentucky says they don't bite. Colorado State says bites have been reported on rare occasions, and Clemson says they occasionally bite when handled, so avoid picking them up.[1][4][5]
- What do baby boxelder bugs look like?
- Nymphs are wingless with bright red abdomens and black legs and antennae, turning darker red as they grow.[3][4]
- How do I get rid of boxelder bugs naturally?
- Spray clusters with laundry detergent and water, vacuum the ones indoors, and seal cracks before fall.[4][3][6]
- Do boxelder bugs damage my house?
- No. They cause no direct damage to the structure, its contents or people, though crushed bugs can stain surfaces and smell.[3][4]
- Why do boxelder bugs show up indoors in winter and spring?
- Bugs sheltering in walls become active on warm, sunny days and can wander into living areas. They leave for host trees as buds open, so Colorado State says the problem should be over by late May.[4][6][2]
Sources
- University of Kentucky Entomology, “ENTFACT-444: Boxelder Bugs.” entomology.mgcafe.uky.edu/ef444 (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pest Notes: Boxelder Bug, Publication 74114 (July 2014).” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnboxelderbug.pdf (accessed 2026-11-11)
- Penn State Extension, “Boxelder Bug.” extension.psu.edu/boxelder-bug (accessed 2026-11-11)
- Colorado State University Extension, “Boxelder Bugs (Fact Sheet).” extension.colostate.edu/resource/boxelder-bug/ (accessed 2026-11-11)
- Clemson Cooperative Extension, Home & Garden Information Center, “Boxelder Bugs (HGIC).” hgic.clemson.edu/factsheet/boxelder-bug/ (accessed 2026-11-11)
- USDA Forest Service, “Forest Insect & Disease Leaflet 95: Boxelder Bugs (Ciesla and Hanavan, revised February 2011).” www.fs.usda.gov/foresthealth/docs/fidls/FIDL-95-BoxelderBugs.pdf (accessed 2026-11-11)
- iNaturalist, “Boisea trivittata taxon page (order and family).” www.inaturalist.org/taxa/53227 (accessed 2026-11-11)