Wood Cockroaches

Summary

Wood cockroaches are native species that are commonly found in forest leaf litter, under logs, and other damp outdoor areas with a lot of decaying organic material. They occasionally come indoors but dehydrate and die quickly so are only considered a nuisance pest because of their presence.

Classification

Common name: Wood cockroaches, North American wood cockroaches

Scientific name Parcoblatta species

Family: Ectobiidae (no common name)

Order: Blattodea (Cockroaches)

Range and Description

Twelve species of Parcoblatta wood cockroaches occur in North America, seven of which are found in Pennsylvania. Adult males are the only life stage that can reliably be identified to species. Adult females and nymphs are difficult or impossible to identify to species. However, natural history of all species is similar so species identification is not necessary for understanding and control of wood cockroaches.

Wood cockroaches have a classic cockroach shape and look, being dorsoventrally flattened with spiny, splayed running legs, long antennae, and a head that is concealed from above. Adult male wood cockroaches grow up to 1 inch (25 mm) long and have longer, thinner abdomens and long wings that cover the abdomen (Figure 1). Females grow up to ¾ of an inch (19 mm), and have wider abdomens and short, non-functional wings that often leave the end of the abdomen exposed (Figure 2). Both males and females are shades of light brown to nearly black. Some species also have cream-colored stripes on edges of the wings and prothorax. Immature wood cockroaches are smaller, lack wings, and are reddish brown to dark brown, with some species being bicolored (Figure 3).

Figure 1. Male wood cockroaches. Note the long wings and differences in coloration from light brown to dark brown. Left to Right: Parcoblatta virginica, photograph by cmciv via iNaturalist, used under a CC BY-NC 4.0 license. Parcoblatta bolliana, photograph by Graham Montgomery via iNaturalist, used under a CC BY-NC 4.0 license. Parcoblatta pennsylvanica, photograph by Brandon Woo via BugGuide, used with permission.

Figure 2. Female wood cockroaches. Note the shorter wings, wider abdomen, and differences in color from reddish brown to dark brown. The individuals on the left and center have oothecae, or egg cases, protruding from the ends of their abdomens. Left to right: Photograph by chipperatl via iNaturalist, used under a CC BY-NC 4.0 license. Photograph by Seig via iNaturalist, used under a CC BY-NC 4.0 license. Photograph by Dave Eib via iNaturalist, used under a CC BY-NC 4.0 license.

Figure 3. Wood cockroach nymph. Note the lack of wings. Photograph by Julian F via iNaturalist, used under a CC BY-NC 4.0 license.

Wood cockroaches may be confused for pestiferous species. American cockroaches are much larger than wood cockroaches (adults up to 2 inches in length) and are reddish-brown in color. Oriental cockroaches are dark brown to nearly black in color; females lack wings, while males have short wings similar to female wood cockroaches. Cockroaches may be difficult to distinguish, so if you are unsure if you have wood cockroaches or a pest cockroach, reach out to your local county extension office for assistance.

Natural history and behavior

Egg capsules (oothecae) are laid in the summer and take about a month to hatch (Figure 4). Nymphs grow throughout the rest of the summer, overwinter, and mature into adults the following spring, although may persist as nymphs for up to two years. Adult wood cockroaches live for many months throughout the summer, but sometimes live for up to two years, so are present throughout the warm months.

Figure 4. Wood cockroach egg case, or ootheca (plural = oothecae). Cockroach species or groups can be identified based on the size and shape of the oothecae. Photograph by MJ Hatfield via BugGuide, used under a CC BY-ND-NC 1.0 license.

Wood cockroaches are typically found outdoors in damp areas with a lot of organic matter, such as in leaf litter, under fallen logs and loose bark, in wood piles, and under stones (Figure 5). They feed on decaying plant matter.

Figure 5. Typical wood cockroach habitat, including leaf litter and fallen and rotting logs. Photograph by Nicholas_T via Flickr, used under a CC BY 2.0 license.

Male wood cockroaches can fly and are sometimes attracted to lights at night in rural areas (Figure 6). In some instances, they have been known to accumulate in clogged rain gutters.

Figure 6. Male wood cockroach attracted to porch lights at night. Photograph by Schmitty via iNaturalist, used under a CC BY-NC 4.0 license.

Damage

Wood cockroaches are not considered pests. Outdoors, they are indicators of a healthy ecosystem and important decomposers. They occasionally come indoors by accident, either through cracks in a building foundation or around windows and doors, on firewood, or after being attracted to porch lights. When this happens, they may be considered a nuisance because of their presence. However, they quickly die within a few days due to dehydration and do not feed or reproduce indoors.

Control

Because wood cockroaches are accidental home invaders, the best control is to exclude from a building in the first place. Depending on how they are entering a building, this might include only bringing in as much firewood indoors as can be burned in a few hours, moving a pile of firewood or piles of debris away from the building, caulking cracks in a foundation or around doors and windows, installing a brush on the undersides of doors, or turning off lights at night so as to not attract flying males. Buildings with cedar shake shingles in wooded areas sometimes have issues with wood cockroaches living under the shingles as these mimic their preferred habitat. In this case, replacing the roof with a different material or trimming or removing trees to increase sunlight and encouraging warm, dry conditions on the roof may be the only long-term solutions available. Because wood cockroaches die quickly indoors, pesticides are not necessary or recommended.

References

Beccaloni, G. W. 2014. Cockroach Species File. Parcoblatta. Version 5.0/5.0. Available online. Accessed 21 February 2023.

BugGuide. 2017. Parcoblatta. Available online. Accessed 21 February 2023.