We’re approaching that time of year when we start to get a flurry of panicky phone calls from residents who are finding cockroaches in their homes…often for the first time ever. In most cases, our inspectors find that the pests in question are wood cockroaches and there is little reason for concern.

Wood roaches are not what we call “domestic” cockroaches, meaning they cannot, and do not, set up housekeeping in your home. These are outdoor cockroaches that are in your home only by accident, and are only temporary pests.

The main wood cockroach in Massachusetts and New Hampshire is the Pennsylvania wood cockroach, Parcoblatta pennsylvanica. These cockroaches are fairly large, close to 1 inch long when fully grown. The male is tan to brown with long wings. The female and the nymphs are dark brown and appear wingless.

Mating Season is the Cause of the Problem

We get most of our wood cockroach calls during the cockroaches’ mating season which is May and June. These roaches are not very obvious at other times of the year. They feed on decaying organic material and are found under bark in woodpiles, stumps, or in hollow trees. Occasionally they are brought inside in firewood, and they like to hide under cedar shake shingles and in roof gutters. They also like damp sheds. But during spring mating season, male wood cockroaches become very active, traveling in groups, and flying long distances in search of a female. Homeowners that live on heavily wooded lots are the most likely to be visited by wood roaches.

There are two reasons that wood cockroaches end up inside in spring. One, the male cockroach flies to lights at night (the female has very short wings and can’t fly). If you have porch lights or yard lights or even bright indoor lights, you may be attracting wood roaches that can enter your home through open doors or windows, or through cracks and crevices.

The second reason that wood cockroaches end up inside is that the male roaches will track a female through the pheromones she releases. If just one random female wood roach manages to find her way into your home, she can be shortly followed by many amorous male roaches.

The Best Control is to Keep Them Outside

Wood cockroaches are rarely able to establish a breeding population indoors. They’re pretty inactive indoors and die in a short time. Indoor pesticide control is usually not necessary, just grab a vacuum. Instead, take measures to keep the roaches from getting inside in the first place.

An exterior perimeter pesticide treatment can keep both sexes from entering (give Colonial Pest a call). Reducing bright lighting (see Porch Lights Attracting Bugs? Choose a Better Bulb) and tightening screens and door thresholds (especially garage doors) will also help to keep wood cockroaches out. Move woodpiles, and leaf and mulch piles away from your home.