Relationships between pretarsus morphology and arboreal life in ponerine ants of the genus Pachycondyla (Formicidae : Ponerinae)

Morphological traits of the pretarsa, especially the tarsal claws and aroli a, of 15 arboreal or ground-dwelling species of the genus Pachycondyla demo nstrate that two types of morphologies exist. All of the arboreal and three of the ground-dwelling species have a well developed in the form of an adh esive pad, whereas the others do not. Moreover, the tarsal claws are spread and horn-shaped in the species of the first group, whereas they are straig ht and relatively close together in the species without the adhesive pad. T he ability to walk upside down is strictly correlated to the presence of th e pad. If a large adhesive pad cannot be considered as a morphological adap tation to arbtored life, it, at least, constitutes an indispensible charact eristic for the advent of arboreal behavior.