Question

We had another pest control company treat our home for cockroaches. The technician said that we had wood cockroaches. We do have a wooded lot but I thought wood cockroaches were the dark brown, wingless roaches that we see inside occasionally. These were light brown and obviously had wings because they were flying all over. I need your second opinion please.

Answer

What you describe is one and the same cockroach, Parcoblatta pennsylvanica, better known as the Pennsylvania wood roach. What you’re seeing is the very obvious difference in appearance between the male and female, uncommon for cockroaches. In fact, the two sexes look so different that they were once described as two different species.

The female wood cockroach is dark brown and about ¾ inch long with a broad body. She isn’t wingless but has very short wings and doesn’t fly. The male wood roach looks very different. He is bigger than our usual German cockroach (about 1 inch long) and straw color to light brown with a pale yellow edge around his body. His body is more of an elongate shape, he has long wings, and he flies. Wood cockroach nymphs are reddish-brown, smaller and wingless versions of the female.

Wood cockroaches are outdoor insects, common in wooded areas where they feed on decaying organic matter. They get into homes accidentally, or when they are lured in by the pheromones of a female wood roach. The good news is that wood cockroaches don’t usually reproduce indoors, and in fact they don’t live very long indoors. They are temporary nuisance pests, usually from late May through June (their mating season), or occasionally in the winter when nymphs are brought indoors on firewood.

You saw male wood cockroaches, but you almost certainly had a female nearby. The reason being that the male roaches would not normally enter your home in any numbers unless they were drawn there by the pheromones of a female roach. One female that crawls or is carried into a house can draw in many males. Since the males fly and are also attracted to yard or porch lights, some may find their way inside as a result. Once inside, the males are usually inactive during the day but fly to lights at night. Unfortunately, it is very difficult to find and eliminate the secretive female that caused the problem. If you have an annual problem with wood roaches, there are a couple of things you can try to reduce their numbers.

How to Keep Wood Cockroaches Out

• Move any woodpiles away from your house and bring in only as much firewood as you need at one time. If you’re really serious, you can debark firewood before bringing it inside.
• Keep piles of mulch and leaf litter away from the house.
• Change or reduce your outside lighting so as not to draw male cockroaches to your door. Direct lights out into the yard, rather than onto the doorstep.
• Seal any openings where the roaches may be entering around pipes, conduits, vents, and screens, and make sure doors (especially garage doors) have thresholds or sweeps.

But if your home is surrounded by woods, you may have to accept the fact that wood cockroaches will be an occasional part of your life.

Photo credit: wwwebber / Foter.com / CC BY-NC-SA