Comparative morphology of second and third instar larvae of Palaeostigus bifoveolatus (Boheman, 1851) (Coleoptera: Staphylinidae: Scydmaeninae)

Abstract

Exoskeletal morphological structures of all extant genera currently included into Mastigitae are very well studied, whereas the larvae are poorly known. Larval morphology provides a valuable character system for phylogenetic reconstructions, and as all hitherto carried out analyses of Mastigitae were based on adult characters only, it is important to fill this major gap by studying immature stages. We here describe in detail the second- and third-instar larvae of the South African ant-like stone beetle Palaeostigus bifoveolatus, including chaetotaxic structures. We attempt to identify novel characters to distinguish larvae of Palaeostigus and Stenomastigus, and instar-specific features. The hypersetation found in P. bifoveolatus supports previous findings of close phylogenetic affinities between Mastigitae and Scydmaenini, and the tendency toward reduction of the antennomere III, from small to vestigial, is also consistent with the current phylogenetic hypotheses regarding these two groups within Scydmaeninae.