Comparative morphology of the feeding apparatus of Staphylinine beetles (Coleoptera: Staphylinidae)

Abstract

The mouthparts and protarsi of adult rove-beetles of the Staphylinine group are examined in detail. We provide descriptions and image plates based on scanning electron micrographs taken from 36 species representing all 10 subfamilies comprising this large staphylinid subunit. We establish groundplan features of the mouthparts for the Staphylinine group and discuss, in detail, aspects and functions of structures that compose the feeding apparatus. A phylogenetic scheme is used to conduct an ancestral character reconstruction of the morphological characters. The potential groundplan features of the characters rendered in our parsimony analysis for the Staphylinine group are: labrum subquadrate or longer than wide; mandible without subapical teeth and retinaculum, with prostheca present, not forming lobe-like projection, and with a mola; maxillary palpomere 4 well-developed, fully sclerotized, similar in width to palpomere 3; ‘glossa’ integrated with prementum plate, sometimes represented by pairs of sensilla basiconica; ‘paraglossa’ with unmodified antero-lateral lobes; labial palpomere 3 from as wide to half as wide as penultimate palpomere. To explain the shape variation of the mandibles, a geometric morphometric analysis was carried out. A character mapping analysis of mandible shapes revealed a trend in the Staphylinine group toward a falcate shape with a narrow base, typically present in some predatory species.