Can you describe cockroach eggs please? I’m trying to get rid of a cockroach infestation in my apartment and I’m not sure if my efforts are killing any cockroach eggs that might be around. I’m assuming that they are tiny and white.

Z. E., Fitchburg, MA

The reason that you don’t know what cockroach eggs look like is that chances are you will never see them. Instead, what you will see is a brown, capsule-shaped, enclosed egg case that holds many cockroach eggs or developing nymphs. Once you see a picture of a cockroach egg case, you’ll say, “oh yeah, I’ve seen those things!”

A COCKROACH EGG CASE IS A PORTABLE NURSERY

I’m assuming that the cockroaches in your apartment are German cockroaches, our most common indoor cockroach. These roaches are about ½-inch long with an egg case that is light tan and about ¼-inch long by 1/8-inch wide. The females of most other cockroach species carry their newly-extruded egg case for a short time, then place it or “glue” it in a hidden, protected place until it hatches, sometimes weeks later. The German cockroach mom, however, takes extra care of her offspring by carrying her egg case, protruding from her abdomen for two to three weeks, until just before it hatches.

Cockroach Egg Case, also known as an ootheca. Shutterstock.

The egg case of the German cockroach has rows of indentations on each side. Each indentation outlines an egg compartment on the inside that will become a developing cockroach nymph. Each egg case can hold a total of 30 to 48 developing nymphs. If you opened the egg case up like a suitcase, you would see 15 to 24 nymphs lined up on both the top half and the bottom half. Eventually, the fully-developed nymphs split open their protective case and look for a hiding place in your kitchen!

Larger cockroach species such as the American or Oriental cockroach produce egg cases with fewer nymphs in each: American cockroach = 14-16 nymphs per egg case, Oriental cockroach = 12-16 nymphs per egg case. The egg case of each species of cockroach has a somewhat different size, shape, and color. Experts can identify the cockroach by looking at an egg case.

EGG CASES MAY NOT BE AFFECTED BY INSECTICIDES

Dead cockroach with egg case attached. Shutterstock.

In a heavy cockroach infestation, you will see both hatched and unhatched egg cases amid the cockroach poop, shed skins, dead bodies, and other debris. An unhatched egg case looks full and plump while one that has hatched may appear split, dented, or crumpled.

You can see why German cockroaches are so successful. They have more nymphs per egg case than any other species and the female can produce 4-8 egg cases in her lifetime. Besides being protected by the female initially, the hardened outer cover of a deposited egg case is naturally resistant to insecticides, so new cockroaches can hatch out days or weeks after a pest control service. You’ll want to make sure that you or your pest control contractor schedule follow-up service to kill any cockroach nymphs that have emerged from egg cases in the meantime.