The emerald cockroach wasp (Ampulex compressa, also known as the jewel wasp) is a parasitoid wasp of the family Ampulicidae. It is known for its reproductive behavior, which involves using a live cockroach (specificially a Periplaneta americana) as a host for its larva. A number of other venomous animals which use live food for their larvae paralyze their prey. Unlike them, Ampulex compressa initially leaves the cockroach mobile, but modifies its behaviour in a unique way.
As early as the 1940s it was published that wasps of this species sting a roach twice, which modifies the behavior of the prey. A recent study using radioactive labeling proved that the wasp stings precisely into specific ganglia. Ampulex compressa delivers an initial sting to a thoracic ganglion of a cockroach to mildly paralyze the front legs of the insect. This facilitates the second sting at a carefully chosen spot in the cockroach’s head ganglia (brain), in the section that controls the escape reflex. As a result of this sting, the cockroach will now fail to produce normal escape responses.
The wasp, which is too small to carry the cockroach, then drives the victim to the wasp’s den, by pulling one of the cockroach’s antennae in a manner similar to a leash. Once they reach the den, the wasp lays an egg on the cockroach’s abdomen and proceeds to fill in the den’s entrance with pebbles, more to keep other predators out than to keep the cockroach in.
The stung cockroach, its escape reflex disabled, will simply rest in the den as the wasp’s egg hatches. A hatched larva chews its way into the abdomen of the cockroach and proceeds to live as an endoparasitoid. Over a period of eight days, the wasp larva consumes the cockroach’s internal organs in an order which guarantees that the cockroach will stay alive, at least until the larva enters the pupal stage and forms a cocoon inside the cockroach’s body. After about four weeks, the fully-grown wasp will emerge from the cockroach’s body to begin its adult life.
The wasp is common in tropical regions (Africa, India and the Pacific islands), and has been introduced to Hawaii by F. X. Williams in 1941 as a method of biocontrol. This was unsuccessful because of the territorial tendencies of the wasp, and the small scale on which they hunt.
Imagine, if you will, how a wasp evolved the ability to perform brain surgery complete with a drug that turns a cockroach into a docile zombie it can lead around like a dog on a leash. I emphasize the word imagine because any story you come up with is a work of fiction. Such fiction is the basis of the Theory of Evolution.