Predatory behavior in the genus Leptogenys: A comparative study

We studied the predatory behavior of seven species of the genus Leptogenys from Mexico and Cameroon. The ants of this genus are armed with long, thin, curved mandibles articulated at the extreme corners of the anterior margin of the head, permitting them easily to seize oniscoid isopods, the obligate or the principal prey of most Leptogenys species. Workers hunt these prey, which ape able to roll themselves up, solitarily. Foraging behavior comprises sequences of up to eight activities. The prey can be seized by the body (rolled up or not), or alternatively by the edge of the shell, then turned over and stung on the ventral face. A relationship between the mandible size of the workers and the handling method permitted us to established that the phase ''seizure by the edge of the shell'' (compared to grasping the prey by the body) was more frequent as the prey size increased or the mandible length of the workers decreased. The rate of prey escape followed the same pattern. When a prey escaped, workers reacted by using a local searching or ''reserve'' behavior: they moved by increasing both sinuosity and speed. Recruitment occurred mainly after a worker found a group of prey or a large prey. L. mexicana are attractive at a distance to the isopods Bathytropidae living in the same natural environment. As a consequence, prey capture is possible without foraging for this species.