Cockroaches develop through a process called gradual metamorphosis. In this process, the immature roaches look almost like the mature roaches. This process has three stages: egg, nymph, and adult.
When the female produces eggs, she forms a protective case called an ootheca around the eggs. In most cockroach species, the female drops the ootheca in a suitable location before the eggs are ready to hatch. The female roach usually drops the egg case near a food source. When they are ready to hatch, the nymphs break out of their eggs and then break out of the ootheca.
Nymphs / Larave
Cockroach nymphs are immature cockroaches. Because the female roaches produce a lot of eggs, if is normal for an infestation to have more nymphs than adult roaches.
Many cockroach nymphs look like tiny versions of the adult roaches. The nymphs do not have wings, but nymphs of many species have similar coloration to the adults. Some species, however, change colors as they develop. American and smokeybrown roaches have markings as nymphs. As they develop, the markings change into the markings of the adult.
As they grow, cockroach nymphs must shed their exoskeleton. This process is known as molting. The nymph develops a new exoskeleton inside of the old one. The new exoskeleton is soft and flexible. It is also white in color.
After molting, the nymph is white-colored for a couple of hours while the new exoskeleton dries. As the exoskeleton hardens, the nymph gets darker until it is the same color as the other nymphs.
The length of the nymph stage depends on the species of roach. It can take almost 2 years for an American roach to develop from an egg to an adult. A German roach can develop in as little as 2 months. However, the amount of food that is available can affect the nymph’s development time.
If food is plentiful, the nymphs will develop quickly. If food is scarce, they will develop slowly. Some nymphs will also eat other nymphs and that will affect the final number of roaches that can reproduce.
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