Myrmecophilic Relationship of Pella (Coleoptera: Staphylinidae) to Lasius fuliginosus (Hymenoptera: Formicidae)

A large number of staphylinid beetles are closely associated with ants and termites (for review see Wilson 1971, Kistner 1979). Those species living with ants are commonly called myremcophiles. At least a few (Atemeles, Lomechusa) have "broken" the communication code of their host species and are thereby able to become completely integrated in the social system of the ants (H611dobler 1967, 1970, 1971). In an attempt to understand the evolutionary pathways of this highly specialized social parasitic behavior, we studied closely related staphylinid species that do not live within the ant society but instead occupy the foraging trails and garbage dumps of an ant nest. Many of such myrmecophilous staphylinids can be found with the formicine ant Lasius fuliginosus and most of them belong to the genus Pella. Apparently these beetles are not endowed with the behavioral repertory that would enable them to live within the ant colony, although they seem to have a close ecological association with ants (H611dobler 1972). Kistner (1971) redefined the genus Zyras and raised the former subgenus Pella to generic rank. The first behavioral observations concerning Pella (=Zyras, Myrmedonia) were published by Wasmann (1886, 1930). He stated that these beetles feed on dead or disabled ants, but that they also lie in wait near the entrance and hunt ants returning to the nest. Furthermore, Wasmann pointed out that because of their generalized and primitive structure these beetles can be regarded as close to the ancestral forms from which some of the more specialized staphylinid myrmecophiles were derived.