German Cockroach

Contact: Eric Day, Manager, Insect Identification Laboratory

August 1996

German Cockroach

SIZE: Adults are about 5/8 inch long (17mm)

COLOR: Adult German cockroaches are light brown except for the shield behind the head marked with two dark stripes, which run lengthwise on the body. Young roaches are wingless and nearly black with a single light stripe running down the middle of the back. Egg capsules are light tan.

DESCRIPTION: German cockroaches, Blattella germanica (L.), are the most common roaches found in houses and restaurants. Most cockroaches have a flattened, oval shape, spiny legs, and long, filamentous antennae. Immature stages are smaller, have undeveloped wings and resemble the adults. They eat food of all kinds and may hitchhike into the house on egg cartons, soft drink cartons, sacks of potatoes or onions, used furniture, beer cases, etc.

HABITAT: They can develop into large populations and live throughout the house, especially in the kitchen and bathroom. During the day, these roaches may be found hiding clustered behind baseboard molding, in cracks around cabinets, closets or pantries, and in and under stoves, refrigerators and dishwashers. When seen during the day in clusters, the population is large.

LIFE CYCLE: German cockroach females, unlike most other roaches, carry the egg capsule protruding from their abdomen until the eggs are ready to hatch. The case is then placed in a secluded location, with the nymphs emerging one to two days later. A female may produce four to six cases during her lifetime, each containing 30 to 40 eggs. Eggs hatch in 28 to 30 days, and nymphs develop in 40 to 125 days. Female roaches live about 200 days and males not as long. The roach produces more eggs and has more generations per year (three to four) than other roaches, and only a few individuals are needed to develop into troublesome infestations.

TYPE OF DAMAGE: Roaches can foul food, damage wallpaper and books, eat glue from furniture, and produce an unpleasant odor. Some homeowners are allergic to roaches. The pests can contaminate food with certain bacterial diseases that result in food poisoning, dysentery, or diarrhea.

CONTROL: German cockroaches can be detected by examining the premises after dark with a flashlight. During the day, probing hiding places with a wire or thin wood strip will expose roaches. Household sprays of 0.1 percent pyrethrins applied to hiding places will flush out roaches, sometimes killing them if they contact the spray.

Inspect sacks, cartons and boxes, etc., brought into the house, and destroy any roaches. Sanitation is critical in roach control. Clean up spilled foods and liquids, avoid leaving scraps of food on unwashed dishes and counter tops, keep food in tightly sealed containers, rinse cans and bottles before putting them in trash and transfer garbage outdoors into roach-proof receptacles.

Insecticides. Apply chemicals at roach hiding places. Enter a dark room quietly, turn on the light and watch where the roaches run. Spot treat these hiding places and known pathways, especially under and behind loose baseboards or molding strips and around pipes or conduits along the walls and through it. Do not treat entire floors, walls or ceilings. Roaches may hide around the kitchen sink or drain board, in cracks underneath cupboards and cabinets, inside the motor compartment of refrigerators, behind window and door frames, in radio and TV cabinets, and around closet and bookcase shelves. Surfaces where food is prepared should not be treated. Roaches in buildings with multiple dwellings usually require the treatment of other units as well.

INTERESTING FACTS: Without food or water, adults may die in two weeks, but they can live a month with water.

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