Do you have black bugs with bright reddish-orange markings all over your screens? Are they congregating above the door constantly in your way? Or maybe they are just sunning themselves on the front of the garage? Yep, I do. Meet the Boxelder Bug.

There are two different species of Boxelder Bug found in the US, but the one I have gathering around my house is the Eastern Boxelder Bug, Boisea trivittata. The word trivittata actually means, “three-lined”, and refers to the three longitudinal reddish lines just behind the critter’s head. Believe it or not, this often-annoying bug is actually a native to North America. It can commonly be found across most of the mid and eastern US, up into Canada, and has even been found as far south as Guatemala!

The Eastern Boxelder Bug is a “True Bug” in the family Rhopalidae. Despite the family commonly being referred to as “Scentless” Plant Bugs, try not to smash them (or accidentally step on them since they are everywhere right now lol). They do smell rather stinky if they get damaged or manhandled. This is one of their natural defenses and one of the reasons so few animals want to eat them. Boxelder Bugs also taste pretty bad (or so I’ve read), which is the other reason so few predators want to eat them and they feel safe having large parties on your windows. They do try to warn you that they smell and taste bad with their bright reddish-orange markings though (warning coloration = “aposematic” coloration in science talk).

Despite being rather annoying in the fall (and often in the spring as well), the Eastern Boxelder Bug is harmless to people. It primarily eats boxelder, maple, soapberry, and ash tree seeds and leaves, which are pretty abundant where I live. While they can cause some discoloration and damage to fruits and fruiting plants, damage is usually minor and often not even notable unless they are feeding in huge numbers or on saplings. So if they mostly eat tree leaves, seeds, or fruits, why do they seem to be trying so hard to get inside the house?

Boxelder Bugs overwinter as adults. Like so many critters this time of year, that means they need to start finding a warm sheltered place to overwinter in. Our houses fit that bill nicely. While normally the Boxelder Bug would try to find shelter for the winter in leaf litter, under logs or rock ledges, or other naturally sheltered spaces, why stay there when humans have built huge, heated structures right next to their food sources? Yeah, if I were a bug, I’d probably prefer the nice warm, dry, human structures to a drafty bed of dry leaves as well. If you want to try and keep them out of your house you work on sealing up cracks or openings that may be in the sidings or roof of your house. Or blocking the huge openings underneath the garage doors… Maybe that’s just my house, but the openings around the bottom of my garage doors are easily big enough for mice to get in… Or a huge cluster of bugs lol. Alternatively, every time they get inside you can just scoop them into a cup, or onto a folded piece of paper, and toss them back outside. Does seem like a losing battle, but I don’t like killing them since they are natives.

Good news though, even though they are everywhere and constantly getting in the house, you do NOT have to worry about them laying eggs in the house. If you were worrying about that, that is lol. There is nothing for them to eat in your house after all. Well, unless you are growing a bunch of maple seedlings in your basement. No judgment, I have way too outdoor plants inside myself…. The Boxelder Bugs are simply looking for a winter hideaway to sleep in. Once situated, they will usually stay mostly out of sight until it starts warming up in the spring. Then they’ll emerge from wherever they were hiding in your house and clamor by the windows wanting to get back outside. Kinda like when you fly down south for a winter vacation, but then want to go back home once you hear the ice is gone…

To read more about Boxelder Bugs, check out: -Bug News: Mating Season!

• Penn State Extension
• University of Minnesota Extension
• iNaturalist

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