E-359 9-05 Cockroaches: Recognition and Control Roger E. Gold1, Kimberly Engler2, Wizzie Brown2 and Michael Merchant3 ased on the fossil record, cockroaches are among some of the oldest surviv- Cockroach Biology and Behavior B ing insects. They are considered to be Cockroaches have flattened oval bodies, and one of the most successful animals on Earth. their heads are concealed from above by a pro- However, most humans consider cockroaches to notum or shield. Cockroaches have long, spiny be nuisance pests, especially when they invade running legs and filamentous antennae. Their human structures. They can be found anywhere color ranges from dark-brown to reddish-brown within a home, since they can squeeze into very and from tan to black. Cockroaches usually have tight spaces. Cockroaches have chewing mouth- wings, but these may be very small in some spe- parts and are omnivorous, so they will feed on cies. In general, females have shorter wings than all foods consumed by humans and animals and do males. even on waste materials. Most cockroach species are nocturnal; they Most humans feel anxiety at the mere sight hide in damp, dark places during the day and of a cockroach. These insects can contaminate search for food at night. Cockroaches visible dur- food and food preparation surfaces with patho- ing the day usually indicate a severe infestation. gens carried on their bodies and legs. These Cockroaches congregate near sources of heat pathogens can cause food poisoning, diarrhea and moisture, which accelerate their growth and and wound infections. Cockroaches also leave an reproductive rates. unpleasant odor on surfaces they have touched. The cockroach lifecycle consists of three Food fouled by this characteristic odor, secreted stages: egg, nymph and adult. After mating, fe- mainly by American, German and Oriental males produce 12 or more eggs in a bean-shaped cockroaches, is unfit for human consumption, capsule (ootheca). Egg-capsule color varies from with odors usually remaining even after food tan to dark-brown to reddish-brown, depending is cooked or processed. Also, evidence suggests upon species. A female cockroach deposits her that feces and cast skins of cockroaches left be- egg capsule in a secluded spot or carries it in her hind in infested buildings are important allergen abdomen until the eggs begin to hatch. After triggers for asthma and respiratory problems, eggs hatch, immature cockroaches (nymphs) especially in children. emerge. Nymphs are smaller than adult cock- roaches and have undeveloped wings. However, 1Professor and Extension Program Leader for Entomology, 2Exten- sion Program Specialist–IPM and 3Urban Entomologist, Texas nymphs live in the same locations as adults and Cooperative Extension, The Texas A&M University System. feed on the same food resources. German Cockroach: Blattella germanica have tan to light-yel- Because they are so common and have high low bands outlining reproductive rates, German cockroaches are the shield behind the one of the most important structure-infesting head. Both male and 1 5 cockroaches. Adults are /2- to /8-inch in length female American cock- and are light-brown with two longitudinal stripes roaches can fly. on the pronotum (see Females produce egg Fig. 1). Both males and cases and carry them females have wings protruding from the extending to the end tip of their abdomens of their abdomens, for about 2 days. Fe- but they do not fly. Figure 2. American cockroach males then conceal the adult. Nymphs have two egg cases in sheltered distinct, dark stripes areas or near the floor, next to a food source. extending longitudinally Young nymphs are grayish-brown, but after down the entire back. the first few molts, they become more reddish- German cockroach brown. Figure 1. German cockroach offspring have a better American cockroaches prefer sites with high adult. chance of surviving humidity. They commonly live outdoors under than do many other cockroach species, since the the bark of trees or in leaf litter and in barns. females carry their egg capsules until the eggs Sewers also provide an excellent habitat, al- are ready to hatch. This type of cockroach also lowing these cockroaches to spread throughout completes its lifecycle faster than do many other campuses and major cities. Adults and nymphs cockroach species, resulting in a faster rate of can move though main sewer pipes and enter reproduction. kitchens or bathrooms through drainage pipes. German cockroaches are mainly indoor pests, Once indoors, these roaches live in areas close to since they cannot tolerate cold temperatures. furnaces or heating ducts. They commonly are found in homes, apart- ments, restaurants, supermarkets, hospitals, and Oriental Cockroach: Blatta orientalis other buildings where food is stored, prepared or Oriental cockroaches are native to the Middle served. Because they are so small, they are easily East; however, they have become distributed introduced into structures. This type of cock- throughout much of the U.S. Adults are 1- to 1 roach gains entry into structures concealed in 1 /4- inches long and are dark-brown. The groceries or luggage or by migrating from other female’s abdomen is broader than the male’s, infested structures. causing it to drag the ground as the insect German cockroaches sometimes are confused moves. Males have short wings covering 75% of with field cockroaches (Blattella vaga). However, the abdomen; however, females have small wings the field cockroach has a dark face and a dark that barely touch the first abdominal segment. median line on the front of its head between Neither sex can fly. Nymphs are wingless and its eyes, lives outdoors and can fly. The field darker colored than adults, but they are shaped cockroach is found in southeast Texas, far-west much the same. Texas, Arizona and California. Unlike other house-infesting species, oriental cockroaches generally have a seasonal develop- American Cockroach: Periplaneta americana ment cycle, with more adults in late spring or American cockroaches are native to Africa early fall, then decreasing populations by late but have spread throughout the United States summer or early fall. through commerce. These cockroaches, also Oriental cockroaches can survive outdoors known as waterbugs or palmetto bugs, are the in a wide range of habitats, but they prefer largest and one of the most common cockroach- areas with high humidity. They live in cool, 1 es in Texas. They reach 1 /2 to 2 inches long moist places, such as beneath leaves, under and are reddish-brown (see Fig. 2). They also porches and in plant compost, basements, cellars and crawl spaces. They usually invade homes through cracks in the foundation, along sewer Management pipes or under doors. These cockroaches cannot climb slick surfaces, so they usually live under General Management Considerations refrigerators, sinks and washing machines. It is easier to prevent cockroach problems than to control infestations once they have Smokybrown Cockroach: Periplaneta fuliginosa become established. Using insecticides alone is Smokybrown cockroaches are native to not always successful in controlling these insects. temperate regions of Asia but are also found in Eliminating sources of food, water and harborage the southeastern U.S. Smokybrown cockroaches on which cockroaches rely makes control tactics are smaller than American cockroaches, rang- more effective. Attention to good sanitation, use 1 1 ing from 1 /4- to 1 /2- inches long. They are of non-chemical control tactics and exclusion are dark- brown to black, and their wings extend important for keeping your home cockroach free. well beyond the abdomen in both sexes (see Fig. Inspection. Before taking steps to con- 3.). Their antennae are as long as or longer than trol cockroaches, you need to identify problem their bodies. areas, so first conduct a quick home inspection. German cockroaches are most likely to reside indoors around kitchens and bathrooms. Check under sinks and in cupboards, closets, cracks and crevices that provide dark hiding places near food or water. Also, check warm spots or areas near food. Look for cracks with tiny black specks (droppings) that indicate cockroach hiding spots. For outdoor species like American, smoky- brown and oriental cockroaches, look in dark, moist areas close to decaying organic food sources, such as in overgrown ground-cover or Figure 3. Smokybrown Figure 4. Smokybrown flower beds and around trees, wood piles or com- cockroach adult. cockroach nymph. post piles. Also, check for leaking roofs, inspect water-meter boxes, and look at sewer lines near your home, especially those with manhole cov- The female carries her egg capsule for 1 to 2 ers, all of which are favored harborage-sites for days before depositing it. Egg capsules are usu- these cockroaches. ally attached to cracks, depressions or corners Cockroach sticky traps are useful inspection of brick or concrete. As nymphs develop, they tools. Traps typically consist of a piece of card- change color. Younger nymphs are identified by board covered with sticky adhesive. Cockroaches two clear bands on the body and by their white- enter traps and get stuck on the adhesive. Traps tipped antennae (see Fig. 4), while older nymphs help identify areas with cockroach infestations are uniformly reddish-brown. and track the effectiveness of control efforts. Smokybrown cockroaches require high Place traps along paths cockroaches may use humidity for survival. They live primarily out- to travel to and from feeding and hiding areas. doors, in wooded areas that provide shade and Traps should be placed touching walls and in moisture. They also seek harborage in protected corners with both ends unobstructed. For active areas around homes (including tree holes and infestations, relocate traps if no cockroaches are mulch) and in buildings and attics. Stacks of caught after two or three nights. lumber and firewood, sewer-access openings and Sanitation. Sanitation is extremely impor- trash piles can contribute to smokybrown cock- tant for successful cockroach management.