Cockroaches develop through a process called gradual metamorphosis. In this process, the immature roaches look very much like the adults. The nymphs develop wings as they mature. Mature roaches have fully developed wings.
When a female cockroach becomes an adult, she is able to produce eggs. Several species of cockroach can produce eggs without being inseminated. This is called parthenogenesis. Most of these unfertilized eggs do not hatch.
Male roaches usually inseminate female cockroaches. After mating once, the female roach can produce several batches of eggs without mating again. The female cockroach produces eggs inside of a protective capsule. The capsule is called an ootheca.
Each species of cockroach produces an ootheca that is unique in shape and color. Most oothecae are about 0.5″ long. The color ranges from tan to black. The eggs are arranged in two rows inside the capsule. The American roach, like many other species, usually has 14-16 eggs inside the ootheca. The German roach usually produces more than 30 eggs in each ootheca.
The female roach finds a dark, quiet location and deposits the egg capsule within a few hours after it is formed. The female roach often leaves the ootheca in a warm, humid location. There is usually a food source near the place where the female roach drops the ootheca.
There are some exceptions to this pattern. Roaches in the Blaberidae family retract the egg case into their body. The nymphs emerge from the female after they hatch from their eggs.
Female brownbanded roaches find warm, dry places to place their egg cases. They usually glue them in high places — on crown moldings, behind picture frames, or on closet shelves.
Female German roaches carry the ootheca on their bodies for the entire month that it takes for the eggs to develop. In heavy infestations, it is common to see female German roaches with egg cases on the back of their abdomens. When the eggs are almost ready to hatch, the female drops the capsule in a crack or crevice. If she is threatened, she will drop the capsule before it is ready to hatch.
When the cockroach eggs are ready, the nymphs break out of the eggshells and the ootheca. They forage for food and develop without any help from an adult cockroach.