It seems like no matter what time of year it is I’ve got bugs in my bathroom when I’m not seeing them anywhere else. It’s gotten so that I hate going in there at night. Why the bathroom? C.C., Boston, MA

You don’t say what kind of insects you’re seeing so let’s assume it’s a variety. The number one reason that insects end up in a bathroom is moisture. Most insects need high humidity or high moisture levels and they die if their environment gets too dry.

MOISTURE AND LIGHTS ATTRACT INSECTS

When outside foundation insects (crickets, sowbugs, earwigs, millipedes, etc.) find their way inside, they search out basements, bathrooms, and laundry rooms that provide the highest humidity levels. There are other insects that end up in bathrooms because they feed on mold. If your bathroom stays really damp or you have a hidden leak, you could have springtails, booklice, and fungus beetles as full-time residents.

Insects also end up in bathrooms because they are attracted there by lights, often nightlights that act as a homing beacon in a dark house. These are usually flying insects, the same ones you could catch in light traps outside: mosquitoes, midges, moths, crane flies, even wood cockroaches. Your problem could be as simple as a bathroom window with a hole in the screen.

DRAIN FLIES LIVE IN BATHROOMS 24/7

There are also flies that are in bathrooms because they feed and reproduce in drains. The larvae of drain or moth flies, and sometimes phorid flies, feed on the scum down inside sink, shower, and tub drains. The tiny, dark flies that emerge will hang around drains and rest on bathroom walls. See Bathroom Flies That Look Like Little Moths?

The final group of pests that end up in bathrooms are predators searching for prey. Spiders and house centipedes establish themselves in bathrooms because bathrooms are good places to find an insect meal. They are there to intercept all of the insects that were attracted by the reasons above. Your bathroom can be a perfect little ecosystem!

HOW CAN YOU KEEP BUGS OUT OF YOUR BATHROOM?

1) Reduce excess moisture by increasing ventilation or using a dehumidifier in extreme cases.

2) Reduce lighting in the bathroom, especially at night. Keep bathroom doors closed if possible or use a nightlight that has a motion sensor.

3) If your bathroom has a window, make sure screens are tight and keep shades or curtains closed at night so that outside insects aren’t attracted by bathroom lights.

4) Keep bathroom drains clean. If drain flies are a problem, call Colonial Pest for a professional biocide drain treatment. Caustic drain cleaners, boiling water, or bleach won’t kill these flies.