Cockroach eggs hatch when the pressure of the hatchlings within becomes too much. Upon emerging from the egg case, or ootheca, this immature form of cockroach is known as a nymph or a baby cockroach. Nymphs are bright white in color initially, some can be a little darker. They enlarge and will harden and darken within hours.
Cockroach nymphs are grayish-brown in color and darken as they progress onto the next nymph stage. The nymphal development to adult ranges in length from months to over a year.
Once the nymph stage is complete, the Cockroach is now fully matured. Adults of many species can be distinguished from nymphs by their larger size and the presence of wings. However, a few species of cockroach, like the Madagascar hissing cockroach, lack wings even as adults.