Venom of a parasitoid wasp induces prolonged grooming in the cockroach

The parasitoid wasp Ampulex compressa hunts cockroaches Periplaneta america na, stinging them first in the thorax and then in the head, the sting penet rating towards the subesophageal ganglion. After being stung the cockroach grooms almost continuously for approximately 30 min, performing all the nor mal components of grooming behavior. This excessive grooming is only seen a fter the head sting and cannot be attributed to stress, to contamination of the body surface or to systemic or peripheral effects. This suggests that the venom is activating a neural network for grooming. We suggest that the venom induces prolonged grooming by stimulating dopamin e receptors in the cockroach, for the following reasons. (1) Reserpine, whi ch causes massive release of monoamines, induces excessive grooming. (2) Do pamine injected into the hemocoel also induces excessive grooming and is si gnificantly more effective than octopamine or serotonin. In addition, the d opamine agonist SKF 82958 induces excessive grooming when injected directly into the subesophageal ganglion. (3) Injection of the dopamine antagonist flupenthixol greatly reduces venom-induced grooming. (4) Dopamine, or a dop amine-like substance, is present in the venom.