Illinois’ Box Elder Bugs Want In Your House–How To Keep Them Out

For something that doesn't bite, sting, spread disease, or attack in any way, box elder bugs are still looked at as invasive pests that most of us would just like to see gone.

They're definitely not beloved by people at our offices, mostly because they've invaded offices and light fixtures throughout the building.

As I sit in my office writing this, I'm being watched.

Not by coworkers, management, or surveillance cameras, but by 6 small, black and red colored bugs that are hanging around the ceiling light fixtures. Normally, we find them in abundance on the west side of our building where they can bask in the warm sun, but these three, along with several dozen others have already come inside to...I don't know...annoy us.

So, what exactly are box elder bugs, and what do you do about them if you find that they're hanging around your place, too?

Why Are They Hanging Around? What Do They Eat? Are They Venomous? Do They Bite? Should I Squish Them? Why Do I Have Them If I've Got No Box Elder Trees?

Wow. You've got lots of questions (I guess I'm actually the one with questions, since I wrote that), so let's get to some of the pertinent answers:

• They're hanging around because when temperatures begin to cool in the fall, they will start to seek out warmer areas. They are most often attracted to buildings with large southern or western exposures because they are warmer than the surrounding area. They are looking cracks and other spaces to squeeze into, and will occasionally make their way indoors until warm weather returns.
• You don't have to have a box elder tree to have box elder bugs. For food, they sometimes feed on maple or ash trees, too. So, no box elder tree---no problem for the bugs.

• They're not venomous at all. A couple of sources I checked said that they can bite "defensively," but other sources say they do not bite at all. The biggest problem box elder bugs can give you is that their poop can stain light-colored surfaces.
• Don't squish them, because they will emit a foul odor, and cause a big stain on whatever you've smashed them on. Your best move is to vacuum them up.
• Once boxelder bugs are in your house, they're relatively good guests, as they don't eat anything, and they don't reproduce inside your home (which is a lot more than I can say about many houseguests we've had over the years).

What's The Difference Between A Box Elder Bug And A Stink Bug?

Other than one of them being happy not to have the word "stink" in their name, there are some other notable differences.

Boxelder Bug (Boisea trivittata):

• Size/Shape: About ½ inch long, flat, elongated oval.
• Color: Black body with bright red or orange lines along the thorax and wings (forms an “X” pattern on the back).
• Habits: Gather in big clusters on sunny walls in fall; invade homes to overwinter.
• Diet: Feed mainly on boxelder, maple, and ash trees (seeds, leaves, flowers).
• Smell: Can release a mild, sweet but unpleasant odor when squished.
• Impact: Mostly nuisance, rarely damages trees and does not harm people, pets, or homes.

Stink Bug (Brown Marmorated Stink Bug – Halyomorpha halys):

• Size/Shape: About ⅝ inch long; shield-shaped body.
• Color: Mottled brown or gray, with lighter and darker patches; looks bulkier than a boxelder bug.
• Habits: Also overwinter indoors; known agricultural pest.
• Diet: Feed on a wide variety of crops (tomatoes, apples, corn, soybeans, etc.), piercing fruit and causing spots.
• Smell: Release a very strong, pungent odor that's much worse than boxelder bugs.
• Impact: Serious pest in agriculture, damaging millions of dollars’ worth of crops each year.