Boxelder bugs are a common nuisance pest in many parts of North America. While they don’t pose any serious threats, these bugs can invade homes in large numbers in the fall as they seek shelters to overwinter. Learning more about boxelder bugs can help you prevent and control infestations. Here are answers to some of the most frequently asked questions about these seasonal pests.

What Are Boxelder Bugs?

Boxelder bugs (Boisea trivittata) are insects that get their common name from their tendency to congregate on boxelder trees. They belong to the family Rhopalidae, which is known as the “scentless plant bugs.” As true bugs, boxelder bugs have piercing-sucking mouthparts and incomplete metamorphosis with egg, nymph, and adult stages.

Adult boxelder bugs are around 1/2 inch long and have elongated, oval-shaped bodies that are black with red-orange markings. They have three visible stripes behind the head and red veins in their wings. The wings lay flat over the abdomen when not in use. Nymphs resemble the wingless adults but are bright red in color initially, darkening as they mature.

What Do Boxelder Bugs Eat?

The primary host plants for boxelder bugs are female boxelder trees. The bugs feed on the seeds within boxelder pods, sucking out the juices with their straw-like mouthparts. They occasionally feed on other trees as well, including maple.

Boxelder bugs don’t eat solid food. They use their piercing mouthparts to pierce plant tissues and suck out nutrients. This is why they are considered nuisance pests rather than damaging pests – their feeding doesn’t usually harm plants significantly.

Where Are Boxelder Bugs Found?

Boxelder bugs are widespread in the United States and southern Canada. Their range corresponds closely with that of boxelder trees, their preferred host. You can find both boxelder trees and bugs in regions including:

Northeastern United States
Midwest
Rocky Mountains
Pacific Northwest

In areas where the climate is suitable, boxelder bugs may be found year-round. But in most locations, the bugs primarily appear in fall as they congregate on and around structures before seeking winter shelter.

When Are Boxelder Bugs Most Active?

Boxelder bugs are most noticeable and problematic during the fall months. As the weather cools, they leave their summer feeding sites in search of protected places to spend the winter. This results in mass congregations of the bugs on the south- and west-facing sides of structures.

The bugs don’t pose a threat at this time of year. But their presence in such large numbers can be a significant nuisance. Homeowners may find thousands of boxelder bugs covering walls, windows, doors, and other surfaces in the fall.

Boxelder bug activity slows down in the winter when the insects become dormant. They remain inactive until warming spring temperatures bring them out of hibernation. Over the summer, the populations disperse and feed until congregating again in the fall.

Why Do Boxelder Bugs Come Inside My House?

In the fall, boxelder bugs instinctively seek out protected sites to safely wait out the winter. They are attracted to the warmth, shelter, and texture of structures. Congregating on vertical surfaces warmed by the sun helps regulate their body temperature.

Cracks, crevices, weep holes, and openings around windows and doors allow the insects entry into attics, wall voids, and living spaces. Large aggregations of boxelder bugs on exterior walls often precede mass migrations inside as the weather cools.

Boxelder bugs don’t intend to infest homes. They are simply driven by instinct to find suitable overwintering sites. Warm temperatures, reduced airflow, and plentiful hiding spots make human-made structures ideal overwintering habitat.

How Do Boxelder Bugs Get Inside My House?

Boxelder bugs use any available openings to gain entry into homes and other buildings. Common entry points include:

Cracks and gaps around windows and doors
Openings around pipes, wires, vents, and utilities
Damaged window and door screens
Chimneys and openings in foundations and siding
Attic and roof vents

In most cases, the bugs wander in accidentally while searching for overwintering sites. But large aggregations clustered around entry points can indicate a developing indoor infestation. Sealing openings before bugs enter is the best prevention.

Can Boxelder Bugs Damage My House or Property?

Boxelder bugs don’t feed on or damage structures. And they don’t bite humans or pets. The only harm boxelder bugs cause is through the nuisance and mess of large aggregations. Some potential problems include:

Staining and spotting from bug waste on surfaces
Getting crushed and leaving stains when entering buildings
Producing a foul smell when crushed
Possible allergic reactions to boxelder bugs in sensitive individuals

The most significant issue boxelder bugs create is the distraction and disgust homeowners experience when large numbers invade their living spaces. Fortunately, the insects don’t reproduce indoors, so indoor populations eventually die off.

How Can I Keep Boxelder Bugs Off My House?

The best way to control boxelder bugs is preventing them from getting indoors in the first place. Since they access buildings through cracks and openings, sealing potential entry points is crucial. Recommendations include:

Caulk and seal gaps around windows, doors, pipes, vents, utilities, and cracks in the foundation
Screen attic and roof vents
Repair damaged window and door screens
Use door sweeps and weatherstripping to seal gaps
Seal openings where utilities enter the structure
Prune back vegetation touching the building

Maintaining a one-foot vegetation-free zone around the structure’s perimeter can also help deter congregation. Remove boxelder trees within 50 feet. Apply repellent insecticides outside before bugs arrive in fall.

How Do I Get Rid of Boxelder Bugs Inside My House?

If boxelder bugs make it into your home, pest control measures include:

Vacuuming to remove loose insects
Washing surfaces with soapy water to eliminate waste and smells
Sealing hiding spots like cracks, voids, curtain rods, and wall hangings
Trapping bugs on glue boards or capturing them in jars for removal
Using desiccant dusts like diatomaceous earth in wall voids and attics

Insecticide sprays and foggers are not very effective against boxelder bugs indoors. Their hiding habits make it hard for insecticides to reach them. The most effective solution is excluding the insects before they can enter and hiding indoor populations.

How Can I Prevent Boxelder Bugs From Coming Back?

Prevent future boxelder bug problems by excluding them before fall migration begins:

Identify and seal entry points in summer/early fall.
Remove boxelder trees and prune vegetation touching the home.
Apply insecticides to outside walls and entry points before migration starts.
Maintain screens in good repair.
Continue sealing any new openings that appear over time.

Ongoing diligence is needed to keep boxelder bugs from invading. But preventing access points, establishing barriers, and maintaining vigilance will significantly limit future problems. Getting a head start on exclusion before they arrive is key.

Conclusion

Boxelder bugs can be annoying and difficult to eliminate once they’ve moved into a structure. But understanding their seasonal patterns allows you to take preventive measures. Concentrate efforts on exclusion before these fall invaders arrive. Seal cracks, screen vents, prune vegetation, and apply barriers outside to deter entry. Catching indoor infestations early and eliminating access to hiding spots will help resolve current or recurring boxelder bug problems. With some diligence, you can keep these seasonal pests from becoming an annual nuisance.

How to Identify Boxelder Bugs

Boxelder bugs can be identified by their distinct appearance, seasonality, and habits. Learning to recognize boxelder bugs is the first step in preventing and managing infestations. Here are some key signs that point to boxelder bugs:

Physical Appearance

Oval-shaped body, about 1/2 inch long
Black body with three prominent red or orange stripes behind the head
Bright red veins in the wings located flat over the abdomen
A long piercing mouthpart (beak) extended forward from the head
Bright red-orange nymphs that turn black with red markings as they mature

Behavior and Habits

aggregates in large groups on vertical surfaces like walls and trees
seeks shelter in cracks, voids, and secluded locations
moves slowly compared to other home invaders
primarily active in fall as they search for overwintering sites
generally leave buildings in the spring once temperatures warm

Locations

found congregating on southern or western exposures that receive warmth from the sun
often cluster on walls, eaves, around doors and windows
may amass on boxelder trees, especially female trees with seed pods
frequently found in attics, wall voids, window and door frames once indoors

Seasonality

mostly noticeable in early fall as they move to winter shelter
remain inactive indoors over the winter months
emerge in spring but quickly disperse to feed
found widely dispersed during the summer
begin migrating back to structures again in fall

If you notice slow-moving black bugs with bold orange stripes on walls or trees in the fall, chances are high they are boxelder bugs. Their appearance, clustering behavior, seasonal patterns, and favored locations are telltale signs of an infestation. Become familiar with their identification traits to detect invasions early.

How Do Boxelder Bugs Reproduce and Grow?

Reproduction and development impact boxelder bug behavior and the timing of infestations. Understanding their life cycle helps explain why populations fluctuate throughout the year. Here’s a look at how boxelder bugs mate, lay eggs, and progress through growth stages:

Mating and Egg Laying

Once temperatures warm in spring, boxelder bugs become active again after overwintering. Adults mate and females lay clusters of eggs on the bark, leaves, seeds, and stems of host trees, especially boxelders.

Females can produce 200-300 eggs over their lifespan. The optimal temperature for egg laying is between 70-85°F. The eggs are pale red and oval, about 1 millimeter long. They hatch in 10-15 days.

Nymph Stage

Newly hatched boxelder bugs are wingless nymphs. Often bright red at first, nymphs darken to black with red markings as they grow over 4-5 weeks. Nymphs feed on seeds, leaves, stems, and sap from host plants, maturing through 4-5 stages called instars.

During this phase, nymphs stay clustered around food sources like female boxelder trees. There can be 2-3 generations per year. The last generation migrates to sheltered overwintering sites in the fall.

Adults

Once fully mature, nymphs molt into winged adults. This final transition takes around 5 weeks. Adults are about 12 millimeters long. Their wings lay flat over the abdomen when not in use.

Adults can survive through winter to mate again the next spring. Most boxelder bugs live for one year, sometimes two. As days shorten in fall, adults start migrating to protected winter shelters.

Dormancy Over Winter

Boxelder bugs spend the cold winter months inactive, tucked away in sheltered spots. They congregate inside wall voids, beneath bark, in piles of rocks or mulch, and other secluded locations.

In warm spells, boxelder bugs may emerge and become active briefly before settling back into dormancy. Once spring arrives, the cycle begins again with adults leaving winter sites to mate and lay eggs.

Understanding this seasonal life cycle helps explain why boxelder bugs suddenly appear in huge numbers in the fall. It also reveals why thorough exclusion before winter is vital to preventing future infestations.

What Attracts Boxelder Bugs?

Boxelder bugs don’t randomly appear inside structures. Certain environmental cues and resources draw them to buildings as overwintering sites. Being aware of these attraction factors can help you take countermeasures.

Warmth

Boxelder bugs need shelter from freezing winter temperatures. They are attracted to the warmth radiating from south- and west-facing walls warmed by the sun. Congregating on warm surfaces helps regulate their body temperature.

Sealing cracks and entry points on heated walls is especially important. Covering Aggregations with a sheet allows sunshine to warm bugs without touching the building.

Texture and Shelter

The textured surface and cracks around brick, stone, and wood exteriors provide good gripping spots for bugs’ feet. Narrow openings give access to voids where they can gather undisturbed. Sealing and caulking eliminates harborage sites.

Boxelder bugs may also cluster in sheltered areas like under eaves, decks, mulch, leaf litter, and vegetation touching the structure. Removing these habitats deters congregation.

Scents

Chemical scents released by boxelder bugs attract others to join the Aggregations. The smell of crushed boxelder bugs also draws in more bugs. Removing Aggregations as they form can help deter this recruitment.

Light

Like many insects, boxelder bugs navigate using light cues. Interior lights visible through windows and gaps attract them at night. Outdoor lighting also pulls in bugs. Managing indoor and exterior lighting can make a structure less appealing.

Familiarity

Once boxelder bugs find a suitable overwintering site, they are likely to return to that same location again in future years through imprinting. Preventing access breaks this cycle and makes other areas more appealing.

CONTROLLING attraction factors involve eliminating resources that draw boxelder bugs to your home. Sealing gaps, altering lighting, removing vegetation, and frequently clearing Aggregations trains the bugs to seek shelter elsewhere next season.

How to Prevent Boxelder Bugs

Preventing boxelder bug infestations requires a proactive approach focused on exclusion. Here are steps you can take to block boxelder bugs before they become a nuisance:

Inspect and Seal Entry Points

In late summer or early fall, inspect inside and outside your home for potential entry points. Use caulk or sealant to fill gaps around:

Windows and doors
Utility openings
Foundation cracks
Fascia and eaves
Siding gaps
Attic and roof vents

Screen any vents that can’t be sealed. Repair damaged window screens that allow bugs to enter.

Install Door Sweeps and Weatherstripping

Add door sweeps and weatherstripping to create a tight seal around doors. Replace worn sweeps and strips that allow gaps. Ensure a tight seal where doors close against jambs.

Prune Nearby Vegetation

Prune any trees, shrubs, or vines touching the structure. Remove foliage back one foot to eliminate contact. Target female boxelder trees especially.

Create Barriers

Apply pest repellent strips or spray barriers around doors, windows, and other potential entry points before migration begins. Diatomaceous earth also deters migration across treated surfaces.

Manage Lighting

Turn off interior lights near windows and gaps at night. Outdoor lighting on porches, patios, and decks also attracts bugs – use bulbs that emit less UV light.

Monitor and Remove Aggregations

Check known congregation areas daily as migration begins. Remove amassing bugs with a vacuum or broom before they enter the structure.

Diligence and preparation are essential to outsmarting boxelder bugs. Focus efforts on sealing cracks, managing outdoor conditions, and stopping them before infestations take hold.

How to Get Rid of Boxelder Bugs

If boxelder bugs make it into your home, you’ll need to both eliminate the immediate infestation and prevent future ones. Combining these tactics provides the best control:

Vacuum Them Up

Use a strong vacuum with a hose attachment to remove lingering bugs inside. This eliminates live bugs while avoiding the mess of crushing them. Empty the vacuum contents outside immediately.

Seal Entry Points

Inspect again for overlooked gaps that may be allowing bugs inside. Caulk, seal, screen, and weatherstrip entry points to prevent more from accessing the structure.

Wash Surfaces

Use soapy water to wash walls, windows, and other surfaces where boxelder bugs have left stains or waste behind. This removes smells and unsightly marks.

Remove Clutter

Boxelder bugs hide in cracks and voids, especially narrow spaces between objects. Reducing clutter eliminates harborage areas.

Apply Desiccant Dust

Puff small amounts of diatomaceous earth into wall voids, around utilities, and in the attic where bugs may be congregating out of sight. The sharp dust will cut their exoskeleton causing dehydration.

Use Traps

Glue boards or other sticky traps can help capture stray bugs still roaming inside. Just be sure to place traps out of reach of children and pets. Jar traps also allow live capture and removal.

Insecticide Treatment

Insecticide sprays and foggers typically aren’t very effective against boxelder bugs inside. Contact insecticides like pyrethroids can kill visible bugs but won’t penetrate deep into voids and cracks.

Prevent Re-Entry

Continue monitoring for Aggregations outside through fall migration season. Seal up any newfound entry points and keep excluding bugs from re-accessing the building.

An IPM approach combines sanitation, exclusion, traps, and targeted insecticide use as needed. Stopping boxelder bugs first requires sealing up all the open invitations into your home.

How to Keep Boxelder Bugs Off Trees

While named for their association with boxelder trees, these bugs feed on several species. Prevent them clustering on landscape trees by:

9 Questions About Boxelder Bugs