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Introduction

Listen closely on an early summer evening and you may hear a tiny thud of impact that continues well into the night. It’s a familiar sound across much of the United States and Canada – the sound of the Pennsylvania wood cockroach hurling itself against your window screens in attraction to the light.

And sometimes, though you may not even notice it at first, those tiny impacts begin to grow in number. Until to your amusement (or horror), you realize that a whole horde of flying roaches is trying to bash its way inside.

Sound like an exaggeration? Not for many homeowners in wooded areas. And not for the Pennsylvania wood roach, for whom this assault is serious business.

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Let’s take a look at this unrelenting little bug, find out if we should be afraid of it, and see what we can do to keep the flying hordes at bay.

Identification

Pennsylvania wood roach male and female, plus egg sac beside a penny for scale
Pennsylvania wood roach female, male, and egg capsule beside a U.S. penny for scale

The Pennsylvania wood roach looks like a lot of other cockroaches.

It’s similar in shape to the American cockroach (but smaller), similar in color and markings to the German cockroach (but much bigger), and nearly identical in every way to the Southern wood cockroach (you have to poke around its body to be absolutely sure).

Catch one and you’ll discover a flat body, long antennae, and six spiny legs used to climb and otherwise scramble around. It will be chestnut brown to tan in color, have mottled markings on the cowl behind its head, and creamy white edging along the front portion of its wings.

The sexes are strikingly easy to tell apart, as well as strikingly different in behavior. Males are larger, about an inch long or so in length with fully developed wings. While females are slightly smaller, with shorter, less-developed wings.

The wings not only help you tell what sex you’re looking at, but which one is to blame for banging at your screens: The female’s shorter wings render her flightless, leaving all the airborne acrobatics to the males.

Where and How They Live

Range & Habitat

Pennsylvania Wood Cockroach Range: Cockroach illustration superimposed over U.S. Map with known distribution
Pennsylvania wood cockroach known distribution (in orange) across the United States.

The Pennsylvania wood cockroach is an abundant, widely dispersed insect with a range that extends from the East Coast to the Midwest, and into southeastern Canada.

It’s found in Alabama, the District of Columbia, Florida, Georgia, Virginia, Illinois, Indiana, Iowa, Kansas, Louisiana, Massachusetts, Maine, Maryland, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, and Wisconsin. As well as the provinces of Ontario and Quebec.

You’re unlikely to find this roach in cities, but in rural timbered areas where it lives and feeds on decaying plant material, especially inside woodpiles, bark, stumps, and hollow trees.

Reproduction

Illustration of Pennsylvania wood cockroach egg sacs on a tree stump
Pennsylvania wood cockroach egg capsules.

If you were to go out searching for them in the wooded or semi-wooded areas around your house, you’d find Pennsylvania wood roaches in three distinct stages of development: Egg sacs (known as oothecae), immature roaches (known as nymphs), and the adults you’re most familiar with.

The egg sacs are deceptive in that they hold not just a single egg, but up to 32 eggs, which take about a month to hatch. Females are prolific in their egg-laying, and can produce nearly a thousand eggs a year.

The nymphal stage typically lasts 10 to 12 months, after which the life of a Pennsylvania wood cockroach is short, lasting only several months. The insects mate from late spring to early summer, their eggs hatch in the summertime, and they reach adulthood in the following spring.

How You’re Likely to Come into Contact with Them

Illustration of 2 wood cockroaches on window screen attracted to the light
Wood cockroaches attracted to the light inside a home.

Though you’re most likely to encounter them late spring to early summer (their mating season), Pennsylvania wood roaches are active all year and can find their way inside your home at any time.

Mating Season

Mating season is when the insects become most obvious, with groups of determined male wood roaches flying in search of females throughout the night. Though it’s not known why exactly, they’re attracted to artificial lights at night, and so begin to swarm the attractive glow around your home.

They’ll head toward your well-lit windows, to windowed doors, to porch and patio lights, lighted pools, landscape lighting, and car headlights. And every chance they get, they’ll try to fly, crawl, or squeeze their way closer toward whatever source of light they find.

For many folks, this is a ritual of summer. For others, something closer to an onslaught.

If you’re of the onslaught opinion, it doesn’t help matters that a sex-crazed Pennsylvania wood cockroach doesn’t care much about the surface on which it lands – for instance, right on you. Or that you live a little horror story every time you grab a flashlight for a simple nighttime stroll.

Other Times of Year

Other times of year, your encounters are likely to include as many nymphs and adult females as with the now less-aggressive males.

You’ll find them in your gutters and potted plants. Under your wood siding, your wooden porch, inside tree stumps, and beneath your cedar shake. And if they’re anywhere around your house at all, you’ll find them in your wood piles, sometimes living in high numbers.

One of their favorite spots, due to the moisture and its delicious decaying bark, is your firewood. They’ll feed and breed underneath the bark and in the decaying organic matter between the wood. Then when you bring the wood inside, you’ll bring in some roaches, too. This is such a common occurrence, it’s the reason most people get them in their homes.

Those roaches that do make their way in on purpose have probably mistaken your house for a fallen tree and an opportunity to nest. To their loss however, the inside of your house is much too dry for them and they rarely breed there, or even live for very long.

Are They Dangerous?

You may know about the many health hazards surrounding certain cockroach species. Cockroaches are capable of carrying infectious diseases, triggering allergies, and even causing asthma.

But the Pennsylvania wood cockroach is more of an occasional nuisance than a threat. Since they feed on decaying plant material, and not the trash, rot, and bacteria-infested remains that roaches like the German or American cockroach do, casual contact with them is not likely to make you ill.

And though their diet includes among other things, decaying wood- they’re not a threat to your wooden structures, siding, or furniture the way that termites are.

Pennsylvania wood roaches are more like unwanted house guests. Who came in without an invitation. And have no idea how to leave.

How to Get Rid of Them

Before heading for the pest control chemicals, keep in mind that the Pennsylvania wood roach is actually a beneficial insect. It breaks down dead and decaying plants and turns them into fertilizer, which is good for the environment. Including the one around your home.

So when you find a loner that’s somehow made its way inside, you may want to simply catch it and usher it into the woods where it belongs. Likewise, if the ones outside aren’t a major problem, there are some simple preventative steps that can reduce the nuisance that they pose.

If you find them ruining your summer however, or terrifying your kids, there are more aggressive ways to get rid of them.

Suggested Products


To Kill Wood Roaches Quickly When They Come Inside

BASF PT P.I. Contact Insecticide

P.I. is a spray insecticide that kills roaches fast. Best when used as a supplement to other treatments, it’s not inexpensive, but far more effective than off-the-shelf sprays.

To Kill Them Outdoors

Bayer Polyzone Suspend Insecticide

When used on exterior foundations, entries, and walls, Suspend insecticidal liquid stops outdoor roaches before they get in. It requires a separate sprayer (see below), and works best alongside a granular outdoor bait like Intice and an outdoor crack and crevice treatment like Delta Dust.

Chapin 1 Gallon Multi-Purpose Sprayer

Liquid pesticides require a separate sprayer. This inexpensive pump sprayer works fine for smaller jobs.

InTice Perimeter Insect Control Bait Granules

InTice is a granular bait that kills roaches outdoors and in spaces like your garage or attic. Used alongside a spray treatment like Bayer Suspend and a crack and crevice treatment like Delta Dust, it can protect the entire perimeter of your home.

Delta Dust Insecticide Dust

Waterproof and long-lasting, Delta Dust is a crack and crevice treatment effective in high-moisture areas such as attics, exterior walls, and plumbing lines. Delta Dust is regulated and unavailable in some areas.

HARRIS Diatomaceous Earth Powder Duster

Insecticidal dusts like CimeXa work best when applied with a duster tool. This inexpensive diatomaceous earth duster works fine with CimeXa, Delta Dust, and other recommended dusts.

A typical strategy begins with the use of liquid pesticides in what’s known as a perimeter or barrier treatment. In this type of treatment, chemicals are applied outside – beneath siding, along foundations and moldings, under eaves and soffits, and sometimes along roof lines. Chemicals may also be applied to areas of your porch or patio that fall under the glow of outdoor lights, the spots insects collect and cause the most trouble.

Granular baits are also effective, especially in combination with sprays. Baits are left in areas like mulch piles where roaches gather, then kill them after being ingested.

The third solution is insecticidal dust, which works best in combination with the two methods above. Applied to cracks and crevices around your home’s foundation and potential entry points, it damages the insects’ exoskeletons, eventually killing them through dehydration. The product Delta Dust is the one you’ll need (it’s the only insecticidal dust that’s waterproof), and you’ll need a duster tool to apply it properly.

When indoor treatments become necessary (far less common since indoor infestations are rare), the same baits and dusts are useful, especially when applied at indoor points of entry like attached garages, and areas that can actually harbor infestations, such as sheds. Areas such as crawl spaces and attics can be “fogged” with an aerosol insecticide when necessary.

If you plan to spray yourself, don’t apply pesticides anywhere near firewood, which can give off toxic fumes when burned. Don’t spray sensitive vegetation, don’t use chemicals in areas where pets and children may come into contact with them, and only use products approved for the purpose at hand.

How to Prevent a Future Infestation

Since it doesn’t really want to infest your home, the Pennsylvania wood cockroach is easier to prevent than the much more dangerous roaches that do. You can usually keep them out and away with some simple precautions:

  • Seal Your Home. Seal cracks and crevices in exterior walls with a weather-resistant silicone caulk. For large gaps, holes and exposed voids in walls or siding, use wads of steel or (preferably) copper mesh, then seal them with a layer of caulk. Repair or replace damaged window screens, place screens over exposed vents, replace worn weatherstripping, and fit doors with thresholds or sweeps.
  • Make Your Home Less Hospitable to Roaches. Store firewood piles away from the house and avoid carrying firewood over from season to season, which reduces the opportunity for annual breeding. Remove decaying leaves from window wells, from underneath porches, from around bulkheads, and from other areas they collect. If you store garbage cans outside, move them to a dry location, or place a dry barrier like gravel underneath them. Look for outdoor water leaks that create artificially moist environments, and repair them. Cap drain traps, and direct overflow water away from your home. Also keep in mind the next time you build or landscape that a wide lawn presents a barrier to roaches that might crawl in from nearby woods.
  • Make Your Home Less Attractive to Mating Males. Dim or reduce the number of outdoor lights, especially around points of entry like windows and doors. Pull shades and curtains at night if you can, and consider replacing white bulbs with yellow ones that reduce light’s visibility to insects.
  • Stop Carrying Roaches In. Avoid storing firewood indoors, including the garage. Examine the firewood you bring in. And if practical, bring in only enough for a day or two, limiting the numbers of roaches that can make their way in at once.

Frequently Asked Questions

Do Pennsylvania Wood Roaches Bite?

They probably could bite if threatened, but are not aggressive insects and certainly don’t see humans as food. You have little to fear from a Pennsylvania wood cockroach bite.

Can Pennsylvania Wood Roaches Fly?

Females and immature roaches (cockroach nymphs) do not fly. But the males do, especially during mating season when you can see them flying toward light sources such as lighted windows and headlights.

Do Pennsylvania Wood Roaches Carry Disease?

Unlike certain indoor cockroach species, the Pennsylvania wood cockroach doesn’t live or feed in bacteria-infested environments. It’s unlikely that encountering one outside or in your home is going to make you sick.

Sources:

  1. McLeod, Robin. (2005) Genus Parcoblatta – Wood Cockroaches. BugGuide. Retrieved from https://bugguide.net/node/view/31624.
  2. Jacobs, Steve. (2013) Insect Advice from Extension – Pennsylvania Wood Cockroaches. Retrieved from https://ento.psu.edu/extension/factsheets/pennsylvania-wood-cockroaches
  3. Larson, Jonathan. Wood Roach. Retrieved from https://communityenvironment.unl.edu/wood-roach-0
  4. Layton, Blake Jr.. Control of Insect Pests In and Around the Home Lawn. Retrieved from http://extension.msstate.edu/publications/publications/control-insect-pests-and-around-the-home-lawn

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