There are more than 3,000 cockroach species living on planet Earth today. They have been around, basically in their present form, for over 300 million years. Cockroaches do not experience the same gestation process as mammals who have live young. Instead they lay eggs, which develop partially on their own and are hatched.
Cockroaches lay their eggs in cases that are formed before depositing them in suitable locations. The case is called an ootheca and it can hold over 30 eggs. It is released by the female and protects the eggs within until they have reached full maturity, and can hatch and live on their own. Some exotic cockroach species do not release the ootheca until the eggs hatch. These roaches appear to undergo live birth, but in fact they do not.
Egg cases, or ootheca, are placed in warm and damp areas where the conditions are right for egg development. Temperatures around 80 degrees are ideal. Depending on the species, the time it takes for eggs to hatch varies tremendously. For example, the American cockroach takes 38 days, and the German cockroach takes 103 days on average. The roach nymphs, which emerge from ootheca, are white in color and do not have the hard shell necessary for their protection. Over the next six months to one year, the roaches will grow and shed their exoskeletons until they achieve the dark, hard-shelled appearance that you might recognize.
As fully formed adults, all but a few species of cockroach form wings and live for a period of 1 1/2 to 2 years. An adult female can lay eggs once every two months with a total of about four ootheca during the course of her lifetime. This means that one pregnant female cockroach can result in over 10,000 offspring in the course of a single year.
After hatching, roach nymphs will stay with their adult mother for up to two days before heading out on their own. Mating occurs with the use of a spermatophore, or sperm container, which is coated with protein. The spermatophore is placed onto the female where the protein is digested and the eggs are fertilized.
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