We have an unused bedroom upstairs where we have stored several boxes of clothes and books, etc. We used to see mouse droppings in that room but not lately. When I went in there yesterday, I saw about a dozen tiny, dark insects on the walls moving slowly, and found some dead ones on the windowsill. They kind of look like beetles. Any ideas what they are?

R. V., Gloucester, MA

There are a number of possibilities, especially in a room that is rarely disturbed. Given your description and the time of year and without an actual specimen, the best guess would be carpet beetles. In spring, carpet beetle adults emerge and head for light (the window) trying to find their way outside (see Carpet Beetles Often Climb Interior Walls in Spring). Carpet beetles are oval, only about the size of the head of a pin, and look black from a distance. Under magnification, most carpet beetles have a calico pattern of different colors.

LINT BEETLES = CARPET BEETLES?

Carpet Beetle Larva. Shutterstock

Most homes have a few carpet beetles in residence because the brown, hairy larvae feed on a wide variety of animal or plant-based materials (see Carpet Beetles Are Not Just in Carpets). Lint, pet hair, dead insects, and food crumbs, especially when hidden in corners or under furniture, provide food for the beetle larvae. But, the fact that you have that many adult beetles present at one time indicates that you likely have an infested item or items in that room, or nearby.

In your case, stored woolen items are a good bet. Could be clothing, extra blankets, or an old rug, for example. It’s only the larval stage that feeds and they are usually hidden in the material, avoiding light. When adult beetles emerge from the pupal stage they instead head to light because, strangely enough, most feed on flower nectar and mate outdoors. They may return inside to lay eggs.

THERE COULD BE A MOUSE–BEETLE CONNECTION

Black Carpet Beetles are often found associated with pelts and dead animals. Shutterstock

To complicate the issue, carpet beetles will also feed on animal carcasses or in bird or animal nests. Could be that you have a dead mouse hidden somewhere in that room or in a wall void, or even in the attic above. Mice also tend to collect and store food near their nest sites so there could be a food cache that is infested with carpet beetles.

Give Colonial Pest a call. Our technicians will verify the identification (save some specimens), then will inspect the suspect room and other areas looking for a food source for carpet beetle larvae. We can also treat to eliminate emerging beetles and to protect any susceptible items. It’s important to take care of the infestation now before the beetles move on to infest other more valuable items in your home…from that prized trophy mount to your antique Oriental rug.