The trap-jaw mechanism in the dacetine ants Daceton armigerum and Strumigenys sp.

摘要: Ants of three different subfamilies, among them the tribe Dacetini, have evolved very fast snapping mandibles called trap-jaws. The two dacetine genera examined, large Daceton and small Strumigenys, employ same mechanism for their mandible strike. Video analysis reveals that, in Strumigenys sp., strike takes less than 2.5 ms. It is released within 5 ms by contact trigger hairs on labrum. ants a catapult to generate such movement. Before strike, are opened wide locked open position labrum, which functions as latch. They stay even when slow closer muscles contract. Upon hair stimulation, labrum pulled backwards small, muscle. thus freed from catch close rapidly. This reflex controlled giant sensory motor neurones labral neuromere that probably monosynaptically coupled. short latency results combination mechanism, muscles, high neuronal conduction velocities synaptic delays. Comparison with trap-jaw ant genus Odontomachus remarkable example convergent evolution.