Emerald cockroach wasp
|Copyright: Enio Branco (Brutamonte)
|Date Taken: 2007-11-21|
|Camera: Sony Cybershot W50|
|Photo Version: Original Version|
|Date Submitted: 2007-11-21 18:35|
|[Note Guidelines] Photographer's Note [Portuguese]|
|Ampulex compressa |
Species: A. compressa
The wasp is common in the tropical regions of South Asia, Africa and the Pacific islands. The flying wasps are more abundant in the warm seasons of the year.
A. compressa 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.
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. In 2007 it was reported that the venom of the wasp blocks receptors for the neurotransmitter octopamine.
The wasp proceeds to chew off half of each of the roach's antennae. 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 a white egg, about 2 mm long, on the roach's abdomen. It then exits and proceeds to fill in the burrow entrance with pebbles, more to keep other predators out than to keep the roach in.
With its escape reflex disabled, the stung roach will simply rest in the burrow as the wasp's egg hatches after about three days. The hatched larva lives and feeds for 4-5 days on the roach, then chews its way into its abdomen 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. Eventually the fully-grown wasp emerges from the roach's body to begin its adult life. Development is faster in the warm season.
Adults live for several months. Mating takes about one minute, and only one mating is necessary for a female wasp to successfully parasitize several dozen roaches.
While a number of venomous animals paralyze prey as live food for their young, Ampulex compressa is different in that it initially leaves the roach mobile and modifies its behavior in a unique way. Several other species of the genus Ampulex show a similar behavior of preying on cockroaches. The wasp's predation appears only to affect the cockroach's escape responses. Research has shown that while a stung roach exhibits drastically reduced survival instincts (such as swimming, or avoiding pain) for approximately 72 hours, motor abilities like flight or flipping over are unimpaired.
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