By Arthur V. Evans

A neighbor recently sought my advice about tiny, scarlet insects scurrying across his deck and up his walls, some of which were no larger than bits of coarsely ground pepper. Some had apparently found their way into his home and congregated in the well-lit windows on the south side of the house. A quick inspection of his home and property confirmed my suspicions; the tiny invaders were boxelder bugs.

For the past few weeks, I had noticed congregations of both adults and nymphs sunning themselves along back fences alleys and in trees growing along roadsides. I assured my neighbor that they posed no threat to property or pets, and that only in large numbers might they cause some damage to some plants.

The eastern boxelder bug, Boisea trivittata, is widespread throughout eastern United States. The wester boxelder bug, B. rubrolineata, is similar in appearance, but its found mainly west of the Rockies.

Adult boxelder bugs are flat, dark-gray insects with three red lines behind the head and may reach ½ inch in length. The thickened portions of their wings are bordered with red, while the membranous tips are blackish. They are strong fliers, flashing their bright red abdomens as they spread their wings and take to the air. Young nymphs are mostly red, but later stages appear darker as their wing pads grow larger. Both adults and nymphs have long, thin antennae.

Hibernating adults leave their winter hideaway with the advent of warm weather in late March or early April. Soon the females begin laying their dark reddish eggs in the crevices of bark on box elder trees and other nearby objects. The eggs hatch in two or three weeks, just as succulent new box elder leaves are beginning to appear. The nymphs eat and grow, shedding their external skeleton five times before becoming a fully winged adult. Up to two generations of boxelder bugs are produced annually.

Both adults and nymphs prefer to feed on the seed-bearing female box elder trees, sucking sap from the new leaves, tender twigs, and developing seeds. They will also attack ash, maple, plum, cherry, apple, and peach trees, as well as grapevines and strawberries. Damage from their feeding activities may cause blotchy yellow patches or brown spots on fruit and leaves. Severe infestations of boxelder bugs can result in misshapen leaves and fruit, but mature and healthy plants seldom suffer any serious harm.

In the late spring and early fall, flying or crawling boxelder bugs converge on stone piles, tree holes, and other protected places, sometimes by the hundreds. They may invade buildings, crowding into cracks and crevices in walls, door and window casings, and around foundations. They do not bite, nor do they damage buildings, furnishings, clothing, or food. However, they will soil curtains and walls with their waste and will definitely leave a stain if crushed.

The best way to keep unwanted boxelder bugs, as well as other insects and spiders, out of your home is by improving security. Replace screens and door sweeps. Repair thresholds and secure pet doors. Apply screens to vents and other openings. Caulk and seal all possible entry sites near doors, windows, crawl spaces, light fixtures, utility pipes or wires, weather boarding, and in areas along the foundation.

For boxelder bugs already in the house, vacuuming, sweeping, or picking them up are the most effective methods for dispatching them. They do not feed on household structures or reproduce indoors, so there is no need to use chemical controls inside the home. Aerosol sprays designed to kill ants and cockroaches are generally ineffective against boxelder bugs.

Removing leaf litter and other debris that serve as egg-laying sites near the base of female (seed-producing) box elder trees will reduce large populations of boxelder bugs outdoors. Eliminate other hiding places, such as piles of boards, rocks, leaves, grass, and other debris close to the house. Clear leaves and grass away from the house, especially on the south and west sides of the structure. Since boxelder bugs prefer to feed and lay their eggs on female box elder trees, plant male box elder trees instead. Male trees, propagated from cuttings taken from other male trees, are purchased from the nursery. These measures will significantly reduce the numbers of boxelder bugs looking to get inside your warm and cozy home.

As with many other insects labeled as “pests,” a little knowledge of their habits can help to reduce costly and sometimes unnecessary reliance upon pesticides, while at the same time raising our levels of tolerance and wonder. To me, this year’s appearance of boxelder bugs is just another marvelous pulse in the seasonal cycle of life. I am not the only one who feels this way. Just ask the folks in Minneota, Minnesota. They celebrate these little creatures each year with Boxelder Bug Days, a fall festival featuring bug races, bug poetry, plays, and other activities. If you can’t beat ‘em, join ‘em!

© 2010, A.V. Evans


  1. Later in the year, we, in Tallahassee, FL, have “tiny, scarlet, mitelike creatures” that are “no larger than coarsely ground pepper” all over our yard, porch and everywhere else outside. They are small enough to crawl through window screens and they are definitely mites, rather than bugs. Obviously not the case here, but I don’t want anyone to assume that they have bugs, rather than mites, if they read this later in the year. They don’t bite or anything, but just the sheer numbers can be annoying and they smear into a reddish color if inadvertantly squashed.

    • Arthur Evans Says:

      You are right Dave! Positive identification is the first step in dealing with any insect or mite infestation. I have slightly edited the essay in an attempt to minimize any confusion.

  2. Glad to find your blog! We use your NWF field guide all the time.

  3. They spend every winter in our root cellar. It always amazes me that they hide so well in the cellar that we never see them, but they come out by the hundreds on warm winter days & sun themselves on the brick front on warm days.I have great photos of them coming out of the cracks around the door. They don’t bother us & we don’t bother them.

  4. Any idea if they eat other insects at all? I have a venus flytrap. One of the mouths had caught a crane fly. Yesterday a boxelder bug crawled up to it and looked to insert its feeding tube into the dead fly. Maybe it was just sucking up the excretions from the flytrap? I’ll post a picture of it on my blog probably later today.

  5. […] Arthur V. Evans, an entomologist (among other noble pursuits according to his website-check out his boxelder article), took a look for me and agrees it is a Boxelder Bug.  But, he said that these bugs do not eat […]

  6. Thanks for the info…..We have had thousands coming from underneath the aluminum siding!!!

  7. Jason Ainslie Says:

    We have the boxelder bug by the thousands in our home – they love the family room with its woodstove and south exposure. Years ago, we had ladybugs living with us in similar sized populations, but our renovations seemed to deter them from coming back. Interestingly, when the ladybugs moved out, that’s when the boxelders appeared. We’ve had them for about two years now, and I find I’m not so fascinated with them anymore. Aside from preventing their entry (the security solution), is there another effective way to reduce their numbers? Thanks!

  8. This is a great time of year to get rid of boxelder bugs. You can find them congregating on a building exterior or a boxelder tree. Spray them en masse with a dish soap / water mix, or a plant-based pesticide, and you will great reduce their numbers for next fall.

  9. Ethan noble Says:

    I too wonder if feast on other insects? I have some under my porch that I’ve noticed congregate around another fellow, dead, boxelder bug. Then the next day feeding on a cricket. It was very strange, maybethey were just sucKing moisture out? It has been kinda dry. It was interesting because I’ve never seen a cannibal bug lol

    • I do believe they will occasionally feed on a fallen comrade.

      • I live in Burlington Vermont and we have been invaded by those little fellows. My neighbors are going crazy. I mentioned that mixing a solution of dish soap and water in a spray bottle will kill them. I noticed that my window screens wouldn’t budge… they were clogged with bits of grass. Only when I pulled them out did I notice lavea of Boxelders. Luckily they only prefer the sunny side of my house. They gave me a good reason to clean my windows.

  10. So many at my place right now, 104 year old house in Saskatchewan, so often they creep in. Weird thing is these bugs seem to have some sort of ‘curiosity’ or ‘intelligence’ about them. Call me crazy but are they self-aware? haha.

  11. Glenda Rice Says:

    this is a bug I only saw a few of last year but I just walked along the sunny side of the house and there is an army of them all along the walls of the exterior of the house. I have never seen this bug in all 38 years I have been in my home.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: