THE MANDIBLE MECHANISM OF THE ANT GENUS ANOCHETUS (HYMENOPTERA, FORMICIDAE) AND THE POSSIBLE EVOLUTION OF TRAP-JAWS

Ants of the genus Anochetus are able to close their mandibles extremel y rapidly when specialized trigger hairs contact a prey object. This s o-called trap-jaw strike takes less than 2.5 ms and the entire reflex can be performed within 5 ms. The trap-jaw design is based on a catapu lt mechanism composed of a large slow closer and a small fast trigger muscle. The reflex is controlled by giant sensory and motor neurons an d is very similar to that described for the ant Odontomachus. We discu ss the similarities and differences between the two genera and propose a sequence of steps that may have led to the evolution of trap-jaws.