The males of one African species form dominance heirarchies and the females preferentially mate with the dominant male. Another variety with species of cockroaches is the respect in which they carry the eff case or ootheca. German cockroaches keep the ootheca extended from their ovipositor, depositing it only when the eggs are ready to hatch. The American cockroach quickly deposits the ootheca, hides it and leaves it to hatch. The ootheca contains from sixteen to thirty-two eggs, depending on species.
Cockroaches are an essential part of the ecosystem.
They can eat a wide range of substances including other cockroaches and waste. Because of the variety of bacteria and protozoans in their gut, they play an important role in the rapid decomposition of forest litter and animal fecal matter. Cockroaches are then food for many animals, including some humans. Household cockroaches have been identified as disease carriers. The insects are also ideal laboratory animals, easy to care for and easy to handle because they do not sting or bite.