Leptogenys chalybaea

This is a complex of four large bluish species currently revised by Kouichi Arimoto (Kyushu University). In Cambodia and Thailand, workers link their bodies in chains during the retrieval of freshly immobilized large millipedes (Peeters & De Greef 2015). Chains are a striking example of cooperation in ants, and this is the first report of a function during the transport of prey.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia. Oriental Region: Cambodia, Thailand.

Biology
Chain behavior in Leptogenys sp. functions for the collective transport of large millipedes (Peeters & De Greef 2015). This bluish species is a swarm raider with a small range of prey: millipedes belonging to four orders, and occasional earthworms. Small prey were carried individually or dragged by a few ants, while chains made it possible to move millipedes weighing up to 16.4 g. Chains (either linear or branched) changed according to obstacles along the way to the nests. Between 2 and 52 workers were observed to drag single prey items, with only a few ants directly grasping the prey. One 15-cm-long millipede was captured rodeo-style after being encircled by 25–30 ants. As it uncurled from a defensive coil, the ants held back except one that tried to sting between its legs. The millipede started thrashing about which caused many ants to attempt stinging.



Many species of Leptogenys with large workers occur in Africa and the Neotropics (Bolton 1975; Lattke 2011), while large millipedes are also distributed on these continents. Yet chain behavior has never been reported outside SE Asia, suggesting that its evolution requires a complex combination of traits (Peeters & De Greef 2015). Four other ponerine genera hunt millipedes solitarily, but chains are not used.

Nomenclature

 *  chalybaea. Lobopelta chalybaea Emery, 1887b: 432 (w.) BORNEO. Combination in Leptogenys (Lobopelta): Emery, 1911d: 102.