TRAP-JAWS REVISITED - THE MANDIBLE MECHANISM OF THE ANT ACANTHOGNATHUS

Ants of the genus Acanthognathus stalk small insects and catch their p rey by a strike with their long, thin mandibles. The mandibles close i n less than 2.5 ms and this movement is controlled by a specialized cl oser muscle. In Acanthognathus, unlike other insects, the mandible clo ser muscle is subdivided into two distinct parts: as in a catapult, a large slow closer muscle contracts in advance and provides the power f or the strike while the mandibles are locked open. When the prey touch es specialized trigger hairs, a small fast closer muscle rapidly unloc ks the mandibles and thus releases the strike. The fast movement is st eadied by large specialized surfaces in the mandible joint and the sen sory-motor reflex is controlled by neurones with particularly large, a nd thus fast-conducting, axons.