German cockroaches are the most widely distributed and common indoor cockroach pests in the United States, and in many other parts of the world. Around a dozen cockroach pest species can be found in the US, but only two species, the German and brown-banded cockroaches, have adapted to living and reproducing entirely within indoor habitats. American cockroaches are the largest bodied cockroach pests in the US, as females grow to be around 2 inches in length, but German cockroaches are relatively small, at only an inch and a half in length. Their small size allows German cockroaches to move through tight spaces in the wall voids of homes.
Many people have likely encountered German cockroaches indoors, and some people who have suffered through infestations may have found that these insect pests are in the habit of congregating into large groups, similar to a swarm. This aggregation behavior occurs due to “aggregation pheromones” that are both emitted and perceived by the antennae of German cockroaches. However, environmental conditions can interfere with the flow of aggregation pheromones. For example, at lower relative humidity grouping is denser than at high relative humidity. This may be due to decreased pheromone flow in particularly moist conditions.
When German cockroaches inhabit unfamiliar indoor conditions, they travel along the edges of rooms in order to learn the layout of a home or building. Once roaches become familiar with their indoor conditions, they begin to venture into open areas in search of food sources. German cockroaches will eat nearly anything that they encounter, including human food scraps, pet food, and book bindings. One study found that German cockroach populations thrive when fed poultry, but not so much when they are fed grains and sugar. German cockroaches are unable to survive outside of human habitats or away from humans, but exposure to cold temperatures will kill the pests most rapidly. In colder regions, German cockroaches are entirely dependent on heated homes and buildings for their survival.
Have you ever found a cockroach as large as 2 inches in body length within your home?