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.
Homeowners who are fighting roaches should eliminate as much of their food as possible. In the kitchen, wipe up spills, put away leftover food promptly, wash dishes before going to bed, and take the trash out regularly.
Around the outside of the house, rake up as many dead leaves as possible. Clean the leaves out of the gutters. Pick up the pet's food dishes after it has finished eating so the roaches cannot eat the leftover food at night.
Cockroach bait is an effective way to control cockroach nymphs. In the kitchen and bathroom, the gel bait and the plastic stations will work well. Granular bait works well outside in flowerbeds and ground cover.
Bait applications require several follow-up treatments to be sure all of the roaches get some of the bait. For this reason, many homeowners prefer to leave cockroach control to the pest control professionals.