German Cockroach
Blatella germanica

How did it get here?

The German cockroach is actually a tropical species whose point of origin may be Southeast Asia. It spread to America aboard the ships of European immigrants sailing to the Colonies. Highly mobile and adaptable to new environments, the species became a household pest worldwide during the 19th century.

How to spot

German cockroaches are nocturnal and secretive. They spend most of their time in cracks or crevices in walls, between cabinets, and under furniture. Signs of cockroaches include carcasses, body parts, shed skins, empty egg cases (amber-colored, ribbed cylinders) and fecal smears (dark smudges).

Habitat characteristics

Cockroaches live where humans dwell. They prefer warm, undisturbed areas with high humidity near a source of water—under sinks, around toilets, and in showers. They eat human food and also non-food items like soap, toothpaste, and glue. Small nymphs can live in a crack as small as 1/32 inch, while adults require one at least 3/16 inch wide.

Life Cycle

Females produce four to eight egg cases, each containing 30 to 40 eggs. They carry the cases until the eggs are within a day or two of hatching, then deposit the cases in a protected site. The development from egg to adult varies with temperature and humidity, but on average it takes 103 days. Three to six generations may be produced per year. Adults can live 100 to 200 days.

Look-alikes and how to distinguish

• American cockroach (see http://pested.unl.edu/chapter3.htm#cock3e)
• Brown-banded cockroach (see http://pested.unl.edu/chapter3.htm#cock3c)
• Oriental cockroach (see http://pested.unl.edu/chapter3.htm#cock3d)
• Wood cockroach (see http://pested.unl.edu/chapter3.htm#cock3f)

Why is this animal a problem?

German cockroaches contaminate food with their droppings. They can transmit bacterial diseases to humans that can cause food poisoning, dysentery, or diarrhea. Many people are allergic to cockroaches, their waste, or their body fragments, and such allergies cause asthma in some children.

Cockroaches can damage household items, eating glue in wallpaper, books, and furniture.

Management approaches

• Eliminate sources of food, water, and shelter. Fix leaks, wash dishes frequently, seal cracks, and eliminate clutter in kitchens, bathrooms, laundry rooms, and basements.
• Total eradication of cockroaches is virtually impossible, but infestations can be managed. Determine the level of infestation by using sticky traps. Kill roaches by trapping or using pesticides, either chemical or biological. Follow all safety instructions for any products you choose. For a comprehensive, informative look at cockroach life cycles and control methods, see the University of Nebraska-Lincoln's cockroach control and identification manual, which can be viewed online at http://pested.unl.edu/cocktoc.htm.