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How to identify it
- Adults are about 1 1/4 to 1 1/2 inches long and one even dark color: Georgia calls it dark cherry to dark red, UC IPM dark brown to mahogany with an almost-black pronotum, and Tennessee shiny dark brown with no color pattern.[1][3][4][5]
- The wings reach the tip of the abdomen in both sexes, which sets the female apart from the Oriental cockroach's short wing pads. Males and females look almost alike; Tennessee notes a notch in the female's last abdominal segment.[3][5][1]
- Young nymphs are dark with white bands across the back and white antenna tips; older nymphs are uniformly reddish brown. First instars are 1/8 to 3/16 inch and don't move far, so finding them suggests an egg case hatched nearby.[1][3][5][4]
- Adults fly, especially on warm, humid evenings, and are attracted to lights.[4][5][2]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| American cockroach | Larger, about 2 inches, reddish brown, with light-colored edges on the pronotum; the smokybrown is slightly smaller and has no light markings.[4][5] |
| Oriental cockroach | About 1 1/4 inches and almost black, with short wings in males and only wing pads in females, and it doesn't fly.[4][5][3] |
Where it lives
Common in the humid Southeast, especially wooded suburbs; in California it has been a nuisance in parts of the south but is now rarely encountered.[1][4]
Biology and life cycle
Night active; it prefers humid harborages protected from drying wind and sometimes shares outdoor sites with American and Oriental cockroaches.[1][2]
It loses water through its body wall more readily than many other cockroaches, so it lives in moist, warm, sheltered spots such as mulch, ground cover, palm fronds and tree holes, and in places that mimic tree holes, like block walls, soffits and attic eaves away from moving air.[5][3][2]
Outdoors it also lives in plantings, planter boxes, woodpiles, garages, wooden decks and debris-filled gutters, favors the upper parts of buildings, and may live under shingles or siding or in trees in summer.[4][5]
Females carry the dark egg case for about a day before dropping it, and eggs hatch in 24 to 70 days depending on temperature. Texas A&M gives an average of 600 days to reach adulthood and an adult life of 3 to 9 months.[4][3]
It is not native to the United States: UGA's urban entomologist says it is believed to come from Japan, and UC IPM calls it invasive. In Tokyo it was the most common cockroach in homes in a 1994 allergy study.[2][4][6]
Parasitic wasps lay their eggs in the egg cases; in a Gainesville, Florida, study about half of the egg cases collected outdoors were parasitized.[2]
Damage and signs
- Mainly a nuisance invader that shelters in attics and other upper areas of homes. A leaking roof penetration that keeps an attic damp can work like a tree hole for them.[4][2]
- In a South Carolina home they hid in water-damaged wall voids, furnace room walls and porch and carport ceiling voids. Tennessee says older brick homes with heavy deciduous tree cover, clutter such as junk piles and planters, and pets are at higher risk.[5]
Health risk
Smokybrown cockroaches produce allergens. In a Japanese study of 171 children with asthma, 16% had antibodies to this species, and one of its allergens turned up in house dust in eight of ten homes; a Korean study found its allergens cross-react strongly with German cockroach and dust mite allergens.[6][7]
Control
Keep them out
Seal cracks and openings to the outside, and look for entry through items brought in, such as boxes and stored goods.[4][5]
Sanitation
Clear leaves, needles, ivy and ground cover within about a foot of the house, trim branches back a foot from the structure, and remove leaf litter, debris and other materials that hold moisture.[5][4]
Pesticides
Apply gel bait in many small, pea-sized dabs or broadcast granular bait where cockroaches are found; adults and large nymphs may be too big for small bait stations.[1][5]
In research summarized by Tennessee, habitat cleanup plus harborage sprays and baits worked better than a perimeter spray alone and lasted twice as long, 60 days compared with 30, and the outdoor work also cut the numbers seen indoors.[5]
UGA's urban entomologist advises against bug bombs, which he says don't work on these roaches, and against spraying everywhere outdoors, which also kills the wasps that parasitize their egg cases.[2]
Spreading north
Tennessee notes that a 1991 cockroach atlas did not include the state in the smokybrown's range. By 2022 pest control professionals in the Chattanooga area were reporting more of them, and one was trapped at a Knoxville home.[5]
In California the trend runs the other way: UC IPM says it was once a nuisance in parts of southern California but is now rarely encountered.[4]
Where sources disagree
Kitchens: Georgia's fact sheet says it is not commonly found in kitchens the way German cockroaches are, while Tennessee says smokybrowns that get indoors are often seen in kitchens, bathrooms, around entry points and in attics.[1][5]
Sewers: Georgia says it is rarely, if ever, found in sewers, while UC IPM says it may occasionally live in municipal sewers.[1][4]
Egg cases: UC IPM gives about 3/8 inch and 40 to 45 nymphs per case, and Tennessee about 0.4 to 0.6 inch and roughly 26 eggs.[4][5]
Development: Texas A&M gives an average of 600 days to adulthood, and Tennessee estimates one to two years from egg to adult.[3][5]
Common questions
- Does a smokybrown cockroach mean my kitchen is infested?
- Usually not. Smokybrowns mostly live outdoors and in attics, crawl spaces and sheds, and Georgia notes they are not kitchen pests the way German cockroaches are, although Tennessee says the ones that get inside are often seen in kitchens and bathrooms.[1][5]
- Is a palmetto bug a smokybrown cockroach?
- Sometimes. Palmetto bug is a regional name for several large winged cockroaches, including the smokybrown, American and Oriental cockroaches; UGA's entomologist thinks it may have started with the Florida woods roach.[2]
Sources
- University of Georgia Center for Urban Agriculture / Georgia IPM, “Cockroach Fact Sheet (2025).” ipm.uga.edu/files/2025/08/cockroach-fact-sheet.pdf (accessed 2026-11-11)
- University of Georgia College of Agricultural and Environmental Sciences, “Is that a roach or a palmetto bug? (CAES Field Report).” fieldreport.caes.uga.edu/news/10444/ (accessed 2026-11-11)
- Texas A&M AgriLife Extension Service, “Cockroach Biology and Management, E-359 (2012).” extensionentomology.tamu.edu/wp-content/uploads/sites/3/2016/07/E-359-Cockroach-biology-and-management-2012.pdf (accessed 2026-11-11)
- University of California Statewide IPM Program, “Cockroaches (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/cockroaches/ (accessed 2026-11-11)
- University of Tennessee Entomology and Plant Pathology, Urban IPM Lab, “The Smokybrown Cockroach, Insec(tc)ure E&PP Info #841, Vol. 3 Issue 10/11 (K. Vail, Oct. 21, 2022).” epp.tennessee.edu/wp-content/uploads/sites/267/2023/11/2022-10SmokybrownV3I10.pdf (accessed 2026-11-11)
- Arerugi, via PubMed, “Sakaguchi et al. (1994), Sensitization to cockroach allergens of asthma patients in Japan.” pubmed.ncbi.nlm.nih.gov/7887806/ (accessed 2026-11-11)
- Clinical and Diagnostic Laboratory Immunology, via PubMed, “Jeong et al. (2004), Allergenic characterization of tropomyosin from the dusky brown cockroach, Periplaneta fuliginosa.” pubmed.ncbi.nlm.nih.gov/15242941/ (accessed 2026-11-11)
- iNaturalist, “Validiblatta fuliginosa taxon page (order and family).” www.inaturalist.org/taxa/1649048 (accessed 2026-10-06)