Emerald cockroach wasp

The emerald cockroach wasp (Ampulex compressa, also known as the jewel wasp) is a parasitoid solitary wasp of the family Ampulicidae. It is known for its unusual reproductive behavior, which involves disabling a live cockroach (specificially a Periplaneta americana) and using it as a host for its larva. It thus belongs to the entomophagous parasites.

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Distribution

The wasp is common in tropical regions (Africa, India and the Pacific islands), and was introduced to Hawaii by F. X. Williams in 1941 as a method of biocontrol. This has been unsuccessful because of the territorial tendencies of the wasp, and the small scale on which they hunt.

Reproductive behavior

A number of venomous animals paralyze prey as live food for their larvae, but unlike them, Ampulex compressa initially leaves the roach mobile, but modifies its behaviour in a unique way.

As early as the 1940s it was published that female wasps of this species sting a roach twice, delivering venom. A recent study^[1] using radioactive labeling proved that the wasp stings precisely into specific ganglia of the roach. She delivers an initial sting to a thoracic ganglion and injects venom to mildly and reversibly paralyze the front legs of the insect. This facilitates the second venomous sting at a carefully chosen spot in the roach's head ganglia (brain), in the section that controls the escape reflex. As a result of this sting, the roach will first groom extensively, and then become sluggish and fail to show normal escape responses.

The wasp, which is too small to carry the roach, then leads the victim to the wasp's burrow, by pulling one of the roach's antennae in a manner similar to a leash. Once they reach the burrow, the wasp lays an egg on the roach's abdomen and proceeds to fill in the burrow entrance with pebbles, more to keep other predators out than to keep the roach in.

The stung roach, its escape reflex disabled, will simply rest in the burrow as the wasp's egg hatches. A hatched larva chews its way into the abdomen of the roach and proceeds to live as an endoparasitoid. Over a period of eight days, the wasp larva consumes the roach's internal organs in an order which guarantees that the roach will stay alive, at least until the larva enters the pupal stage and forms a cocoon inside the roach's body. After about four weeks, the fully-grown wasp emerges from the roach's body to begin its adult life.

In 2007 it was reported that the venom of the wasp blocks receptors for the neurotransmitter octopamine .^[2]

Pop culture allusions

The creature is often compared to (and sometimes given as a source of inspiration for) many parasites and parasitoids in science fiction. Some examples are as follows.

• Headcrab - From the video computer game series Half-Life
• The Flood - From the video game series Halo
• Goa'uld - From the TV show and movie Stargate SG-1 and its spinoffs
• Yeerk - From the Animorphs franchise
• Facehugger - From the Alien series of films

References

1. ^ *Gal Haspel, Lior Ann Rosenberg & Frederic Libersat (2003): Direct Injection of Venom by a Predatory Wasp into Cockroach Brain, Journal of Neurobiology, 56 (4):287-292 doi:10.1002/neu.10238
2. ^ How to make a zombie cockroach, Nature News, 29 September 2007

• Williams, F. X. (1942) Ampulex compressa (Fabr.), a cockroach-hunting wasp introduced from New Caledonia into Hawaii. Proc. Hawaiian Entomological Society, 11:221–233.
• Ram Gal, Lior Ann Rosenberg & Frederic Libersat (2005): Parasitoid wasp uses a venom cocktail injected into the brain to manipulate the behavior and metabolism of its cockroach prey. Archives of Insect Biochemistry and Physiology 60(4): 198-208 doi:10.1002/arch.20092