Cockroaches frighten many people. They can carry diseases and trigger allergies and asthma. They look scary and “gross-out” most people. To make things worse, they seem to keep coming back, no matter how hard people try to eliminate them.
One of the reasons cockroaches keep coming back is the way they produce their eggs. Female cockroaches make a hard egg case, called an ootheca. Cockroach oothecae are capsule-shaped. Most of them are less than 0.5″ long. They are usually dark brown in color, but some can be tan or black.
Many types of roaches drop the ootheca in a humid area and leave it. Some roaches glue the ootheca to a hard surface so it can't be removed until the eggs inside it hatch. These roaches usually produce 16-20 eggs in each ootheca.
These roaches do not go back to the ootheca after they drop it or glue it. When the nymphs inside are ready to hatch, they come out of the ootheca. They find some type of food nearby. Cockroach nymphs can develop without contact with an adult roach. If the adult roach is killed, the eggs will still develop and hatch.
Some cockroaches, like the German roaches, keep the ootheca attached to their bodies until the eggs inside are ready to hatch. The female German roaches spend most of their time hiding while they are carrying an ootheca. If the female German roach is in danger, she will often drop the ootheca, even if it is not quite ready to hatch. Some of these oothecae hatch after the female roach is killed.
Because the German roaches keep the ootheca attached, they seem to have a very reproductive rate. There are usually 30-40 nymphs in the German roach ootheca, so they can have a lot of offspring. Since they stay in dark cracks and crevices, there are often many more roaches that people do not see.
Homeowners who have been fighting cockroaches should be on the lookout for egg cases. They can be found in areas where cockroaches would hide. It is very important to recognize the oothecae and to remove them. This will be a big step in preventing a re-infestation.