Roach bait

Roach bait describes the most effective method used to kill roaches, taking advantage of the fact that roaches are cannibals.

Since roaches actually live in nests, it isn't enough to simply kill the one or two roaches that happen to wander into a trap, as plenty of others won't. Even if all adult roaches outside the nest are killed, some live eggs will remain in the nest and eventually hatch, which will leave you with the same problem you had before.

So, in order to kill the nest, roach baits don't actually trap any roaches. Instead, the bait lures roaches to eat a "tasty" morsel of concentrated slow acting poison. (Alternatively, the bait may lure the roach so that slow acting contact poison adheres to its body.) The roach then returns to the nest, eventually dying. However, the poison remains in (or on) its body, which the other roaches in the nest soon eat, becoming poisoned as well. In this way, each roach not only becomes a dead roach crawling, but also acts like a Typhoid Mary to the other roaches. Eventually the nest fills up with poisonous carcasses, turning the nest itself into a death trap.