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:
Reproduction
Male roaches usually inseminate female cockroaches. After mating once, the female roach can produce several batches of eggs without mating again.
Eggs
When the female produces eggs, she forms a protective case called an ootheca around the eggs.
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.
Photo credit:https://extension.umn.edu/
In most cockroach species, the female drops the ootheca in a suitable location before the eggs are ready to hatch. The female roach often leaves the ootheca in a warm, humid location. They usually glue them in high places — on crown moldings, behind picture frames, or on closet shelves.
There is usually a food source near the place where the female roach drops the ootheca.
German Cockroach Eggs
There are some exceptions to this pattern. Roaches in the Blaberidae family retract the egg case into their body. 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 they are ready to hatch, the nymphs break out of their eggs and then break out of the ootheca.
Can You See Cockroach Eggs?
Typically ranging from five to 10 millimeters long, cockroach egg cases are easily visible to the naked eye and generally resemble kidney beans in shape. Each case contains an of average of 16 to 37 eggs, with the prolific German cockroach often producing up to 40 eggs at a time.
Hard to Find
Though large enough to be seen, egg cases frequently escape human detection, as female cockroaches either carry the oothecae until just before the eggs hatch (German cockroaches) or lay the capsules in sheltered areas like cracks, crevices, and debris on the floor. Brown-banded cockroaches even glue their egg cases to ceilings, doors, picture frames, and the undersides of furniture.
Nymphs / Larvae
Cockroach nymphs are immature cockroaches. Because the female roaches produce a lot of eggs, it is normal for an infestation to have more nymphs than adult roaches.
What do the nymphs look like?
Many cockroach nymphs look like tiny versions of the adult roaches.
Photo credit:https://njaes.rutgers.edu
Appearance
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.
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.
Diet & Growth
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.
Molting
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.
Adult
Adult cockroaches vary in size according to species. American and Oriental cockroaches are the largest cockroach species in most areas as both exceed an inch in length as adults. German and brown-banded cockroaches are generally about a half-inch long.
Lifespan
The American cockroach typically lives the longest, with a lifespan often lasting up to three years from egg to adult. Oriental cockroaches frequently live longer than a year as well, while the life expectancies of German and brown-banded species usually fall within a year or less.
Because adult female cockroaches produce egg cases repeatedly over relatively short lengths of time throughout their lives, professional pest control services often represent the best option for eliminating infestations caused by the fast reproductive potential of cockroaches.