Description

The Pennsylvania wood roach, Parcoblatta pensylvanica, is a medium sized, light brown cockroach, 1/2 to 3/4 of an inch (12 to 18 mm) long as adults. They are often confused with German cockroaches (Blattella germanica) based only on size, but Pennsylvania wood roaches lack the two lateral black stipes that are present on the top of German cockroaches’ thoraxes. The color of adult Pennsylvania wood roaches is darker brown than that of adult German cockroaches. As adults, both sexes of the Pennsylvania wood roach possess waxy looking hind wings. But adults are sexually dimorphic, meaning the appearances of females and males are different. Females have short, stubby forewings and hind wings that don’t completely cover the abdomen, leaving half of the abdomen exposed. Male hind wings completely cover the abdomen. The thorax and wings have a translucent, pale marginal border around the perimeter of the body. The antennae are the same length as the body or slightly longer. Young nymphs are entirely brown and become darker and develop the characteristic marginal pale border as they mature. The size and orientation of the dark compound eyes give the head an overall dark appearance.

At least six, and possibly as many as eight species of wood cockroaches in the genus Parcoblatta occur in Louisiana, but P. pensylvanica is the most common and frequently encountered species. The southern wood cockroach (Parcoblatta divisa) is extremely similar in external appearance. Separating species within the genus requires diagnostic expertise, but the habits of all species are similar, and the Pennsylvania wood roach serves as a typical example of the group.

The specific epithet “pensylvanica” is often spelled “pennsylvanica.” The spelling presented by the Integrated Taxonomic Information System is used here. The spelling of scientific names is dictated by that used in the original description, in this case by Charles DeGeer in 1773. Apparent misspellings cannot simply be corrected in subsequent uses of the name.

Biology

The Pennsylvania wood roach is found throughout the United States and southern Canada. It is an outdoor species found in forests typically around dead, rotting wood. Individuals may also be encountered on tree trunks and foliage, especially at night, and are strongly attracted to artificial lights. Individuals are often transported into homes via firewood, decorative wood items, camping equipment, and clothing. They are omnivorous and mainly subsist on dead organic matter. They will also feed on a wide range of household food, pet foods and stored products if given the opportunity. A mature female can produce multiple oothecae (egg cases) of 20 to 30 eggs per ootheca. Nymphs can take up to one year to reach sexual maturity, with the length dependent on temperature and humidity. Once males reach sexual maturity, they may congregate at night in the warmer summer months around outdoor light fixtures while searching for females.

Pest Status

Although this species of cockroach may be a nuisance like some other cockroach species found in homes, the long reproductive cycle prevents it from being a serious pest. However, mature adult females can produce many oothecae and hundreds of offspring per season. Infestations are typically associated with environmental factors such as nearby woody debris, unmanaged gardens and flowerbeds, and infested wood being brought into the home. If food and unpackaged stored products are available, populations may build up indoors and require treatment.

Control

Various insecticide baits and general pest control options are available for control of the Pennsylvania wood roach. However, the easiest and cheapest option is ensuring that any wood brought into the home has been properly heat treated or dried. Removing dead foliage and plant matter from gardens or the home perimeter will mitigate areas that wood roaches use as harborages. If cockroaches and other insects are present around outdoor lights, a simple solution is to turn off the lights. Failing that, using green or non-blue and non-UV emitting lights will help prevent insect aggregations. A good alternative for outdoor lighting is yellow-colored compact fluorescent light. These lights are designed to produce light that insects are less attracted to because it’s outside their visible spectrum of light wavelengths.

References

Atkinson, Thomas H., Philip G. Koehler, and Richard S. Patterson. 1991. Catalog and Atlas of the Cockroaches of North America North of Mexico. Miscellaneous Publications of the Entomological Society of America, no. 78. 1-85.

Cochran, D. G. 1986. Biological parameters of reproduction in Parcoblatta cockroaches (Dictyoptera: Blattellidae). Annals of the Entomological Society of America 79: 861-864.

Lawson, Fred A. 1967. Ecological and collecting notes on eight species of Parcoblatta (Orthoptera: Blattidae) and certain other cockroaches. Journal of the Kansas Entomological Society 40: 267–269.

Zemel, R. S., Houghton, D. C. 2017. The Ability of Specific-wavelength LED Lights in Attracting Night-flying Insects. Great Lakes Entomologist 50: 79–85.

Authors:

Steven Richardson, Forest Huval, Chris Carlton