Cockroaches prefer other food sources, but they will eat each other as a last resort when food supplies are scarce or the cockroach population becomes too large.
Most species of cockroach prefer more regular starchy and sweet foods, but if standard food sources are not available they may next move to other organic materials such as toothpaste, glue, or paper as a source of food.
When desperate, hungry cockroaches will also chew on the legs and antennae of other cockroaches that they come in contact with.
Adult cockroaches are also known to eat cockroach nymphs or eggs, which are contained in a suitcase like apparatus called an ootheca that is ejected by the adult female cockroach.
So, although cannibalism may not be a cockroach’s first choice, they are very hardy creatures that will each other if they need to in order to survive.