On this page
How to identify it
- Adults are about half an inch long (up to 5/8 inch) and light brown.[1][2][7][8]
- Two dark stripes run lengthwise on the shield-shaped plate behind the head (the pronotum).[1][2][7][9][8]
- Females carry a light beige egg case about a quarter inch long protruding from the tip of the abdomen until a day or two before it hatches. Penn State describes it as purse-shaped, light brown and less than 1/4 inch long, with two rows of eggs inside.[1][7]
- Nymphs look like small adults without fully developed wings, and they are usually the most common stage you will see. Kentucky and Minnesota add that nymphs are darker than adults, with a light stripe down the middle of the back.[1][9][8]
- Adults have fully developed wings, but Penn State says they do not fly.[7]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Brownbanded cockroach | Also about half an inch long, but with light-colored bands across the wings and abdomen instead of two dark stripes behind the head, and it hides around electronics, wall hangings and furniture rather than mainly in kitchens. Kentucky describes a black, bell-shaped mark behind the head and two yellowish bands across the wings, with egg capsules glued to hidden surfaces such as the undersides of dressers and tables. Minnesota says the two species are rarely found together.[1][9][8] |
| Field cockroach | Lives outdoors; olive-colored, with a black stripe between the eyes on the front of the head.[1] |
Where it lives
Lives indoors, mainly in kitchens, bathrooms and food-storage areas; it prefers warm (70 to 75°F), humid spots close to food, water and dark hiding places, and heavy infestations spread to other parts of a building.[1][2]
Biology and life cycle
Each egg case holds about 30 young, and a female can produce a new egg case every few weeks; a single female and her offspring can produce more than 30,000 cockroaches in a year.[1]
Sources give different breeding numbers. Penn State says each capsule holds up to 48 eggs (usually 30 to 48), a female makes four to eight capsules in her life, about one every 6 weeks at room temperature, and over 10,000 descendants can be produced in a year assuming two generations. Minnesota says females produce about 30 to 50 eggs at a time and six to eight egg cases in a lifetime, and Kentucky says one mated female can produce thousands of cockroaches in less than a year.[7][8][9]
Nymphs go through gradual metamorphosis, growing into adults that have similar habits; the egg case incubates for about 30 days and is carried by the female for most of that time. Penn State says it usually takes 28 days for a capsule to hatch from the time it starts to form.[1][7]
Nymphs pass through six to seven stages over 6 to 31 weeks, according to Penn State; Minnesota says a nymph reaches maturity in about 40 to 125 days. Adult females live 20 to 30 weeks (Penn State) or about 200 days (Minnesota).[7][8]
Like most cockroaches, it is active at night and hides by day in moist, dark cracks near food and water, such as around sinks, appliances and water heaters.[1][2][7][9]
Adults can hide in a crack 1/16 inch wide. Kentucky lists cracks under sinks and toilets, spaces behind refrigerators, dishwashers and stoves, cabinets and pantries, and warm electronics such as clocks and toaster ovens as favorite hiding places.[1][9]
They usually arrive in grocery bags, beverage cartons, boxes, suitcases or furniture, and in apartment buildings they travel between units through shared walls, ceilings, pipes and wires, so even clean homes can become infested.[9][7]
Damage and signs
- Signs of an infestation include fecal specks, shed skins, empty egg cases and dead cockroaches gathered where they hide and breed. Kentucky describes the droppings as pepper-like specks where cockroaches gather.[1][9]
- Cockroaches contaminate surfaces and food; their shed skins and droppings become airborne allergens. Penn State says their odorous secretions can affect the flavor of food and, in heavy infestations, leave a characteristic smell.[1][2][7][8]
- They also damage fabric and paper products and leave stains and unpleasant odors on surfaces they touch.[1][8]
Health risk
In a study of 476 inner-city children with asthma, those who were both allergic to cockroach allergen and exposed to high levels of it in bedroom dust had more asthma hospitalizations, unscheduled medical visits and days of wheezing than the other children. A 2019 review found at least 61 bacterial species reported on German cockroaches, the widest range of any cockroach species it covered, and said these bacteria may help spread foodborne and hospital infections.[11][12]
Control
Keep them out
Seal cracks and false-bottom cupboards and hollow spaces where they hide, and do not keep cardboard boxes and paper bags as long-term storage. Minnesota suggests steel wool or another rough material where plumbing or wiring goes through walls, and covers (escutcheon plates) where pipes enter the wall.[1][2][8][9]
Sanitation
Store food in insect-proof containers, clean up spills right away, take out trash regularly, fix plumbing leaks and other moisture sources, and vacuum cracks and crevices (a HEPA filter keeps allergens from blowing back out). Penn State adds: don't leave dirty dishes out overnight, and empty garbage each evening into a sturdy container with a tight lid. Minnesota says not to leave pet food and water out overnight.[1][2][7][8][9]
Traps and physical control
Sticky traps are the best way to find out where cockroaches are concentrated and to check whether treatment is working; place several and inspect them regularly. Penn State says a week of trapping at ten or more spots usually gives enough information, and Minnesota says to set traps tight against walls and edges.[1][2][7][8]
Cockroaches found on small items such as a toaster or clock can be killed by sealing the item in a plastic bag and putting it in the freezer; in winter, Minnesota says the bag can go outside when temperatures are near 0°F. Leave it in the cold for 5 days, then clean the item before bringing it back in.[8]
Pesticides
Baits are the primary control tool: gel baits applied in small dabs in cracks and crevices, and bait stations, which keep the insecticide in a contained device. Boric acid dust in dry, enclosed voids also works, though slowly, and may take 7 days or more.[1][2][7][8][9]
Kentucky says many small, pea-sized dabs of gel bait in cracks, corners and edges work better than a few large globs, that a cockroach that eats bait usually dies within 1 to 3 days, and that numbers should drop a lot within a few weeks. Don't spray cleaners or other insecticides around bait placements, because that can keep cockroaches from feeding.[9]
Dusts such as boric acid work best as a light film; cockroaches avoid heavy piles of powder. Kentucky says a good deposit is barely visible and should never go on countertops or food-preparation surfaces, and Penn State warns that boric acid can be a hazard to children, so keep treated areas out of their reach.[7][9]
Insecticide sprays alone will not eliminate German cockroaches, and total-release foggers are often ineffective because they do not reach the cracks where cockroaches hide. Penn State and Kentucky add that sprays and foggers can scatter cockroaches deeper into walls, and Minnesota says foggers also raise exposure for people and pets.[1][7][8][9]
When to call a professional
If populations persist despite baiting and sanitation, re-check for other food, water and entry points; some effective baits are sold only to licensed professionals. Minnesota says apartment infestations usually need the infested unit and all neighboring units treated, with help from a pest management service.[1][8]
Where sources disagree
Family: Mississippi State University Extension, GBIF and a 2019 review in the Journal of Medical Entomology place the German cockroach in the family Ectobiidae, while iNaturalist and the ITIS database still list it under Blattellidae.[3][4][12][6][5]
Common questions
- How do I know if it's a German cockroach?
- Look for a light brown cockroach about half an inch long with two dark stripes behind the head, usually in the kitchen or bathroom.[1][2][7][9]
- Why do German cockroaches spread so fast?
- A female can make a new egg case of about 30 young every few weeks, so one female and her offspring can number over 30,000 in a year. Penn State's figures are lower (about 10,000 descendants a year), but every source agrees it breeds faster than other common cockroaches.[1][7][8]
- Do bug bombs work on German cockroaches?
- Usually not. Total-release foggers don't reach the cracks where cockroaches hide, and sprays alone will not eliminate them; baits plus sanitation work better.[1][7][8][9]
- Can German cockroaches cause asthma?
- They can make asthma worse. In a large study of inner-city children with asthma, those allergic to cockroaches who also had high cockroach allergen levels in their bedrooms were hospitalized for asthma more often and had more wheezing days.[11]
- Do German cockroaches live outdoors?
- No. Kentucky says it does not occur outdoors, and Mississippi State says German cockroaches only live indoors, which is why they turn up in kitchens and bathrooms rather than in yards.[9][10]
- Can German cockroaches fly?
- No. Adults have fully developed wings, but Penn State says they do not fly.[7]
Sources
- University of California Statewide IPM Program, “Pest Notes: Cockroaches, Publication 7467 (revised December 2019).” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pncockroaches.pdf (accessed 2026-11-11)
- Utah State University Extension, “German Cockroach (Nuisance Pest IPM Notes).” extension.usu.edu/pests/ipm/notes_nuisance/german-cockroach (accessed 2026-11-11)
- Mississippi State University Extension Service, “German Cockroach, Bug's Eye View Vol. 6, No. 14.” extension.msstate.edu/newsletters/bugs-eye-view/2020/german-cockroach-vol-6-no-14 (accessed 2026-11-11)
- Global Biodiversity Information Facility (GBIF), “Blattella germanica (Linnaeus, 1767) (GBIF Backbone Taxonomy).” api.gbif.org/v1/species/1997215 (accessed 2026-11-11)
- Integrated Taxonomic Information System (ITIS), “Blattella germanica (Linnaeus, 1767), TSN 102415.” www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=102415 (accessed 2026-11-11)
- iNaturalist, “Blattella germanica taxon page (order and family).” www.inaturalist.org/taxa/121237-Blattella-germanica (accessed 2026-11-11)
- Penn State Extension, “German Cockroaches (S. Jacobs).” extension.psu.edu/german-cockroaches (accessed 2026-11-11)
- University of Minnesota Extension, “Cockroaches.” extension.umn.edu/insects-infest-homes/cockroaches (accessed 2026-11-11)
- University of Kentucky Entomology, “ENTFACT-614: Cockroach Elimination in Homes and Apartments (M. F. Potter).” entomology.mgcafe.uky.edu/ef614 (accessed 2026-11-11)
- Mississippi State University Extension Service, “American Cockroach, Bug's Eye View Vol. 5, No. 25 (B. Layton).” extension.msstate.edu/newsletters/bugs-eye-view/2019/american-cockroach-vol-5-no-25 (accessed 2026-11-11)
- New England Journal of Medicine, via PubMed, “Rosenstreich et al. (1997), The role of cockroach allergy and exposure to cockroach allergen in causing morbidity among inner-city children with asthma, N Engl J Med 336(19):1356-1363.” pubmed.ncbi.nlm.nih.gov/9134876/ (accessed 2026-11-11)
- Journal of Medical Entomology, via PubMed, “Nasirian (2019), Contamination of cockroaches (Insecta: Blattaria) by medically important bacteriae: a systematic review and meta-analysis, J Med Entomol 56(6):1534-1554.” pubmed.ncbi.nlm.nih.gov/31219601/ (accessed 2026-11-11)