Morphology of immature stages of Prostomis mandibularis (Coleoptera: Tenebrionoidea: Prostomidae)

Abstract

Structural features of larvae and pupae of Prostomis mandibularis are described in detail. Larval features are discussed with respect to their functional and phylogenetic significance. The distinct asymmetry of the larval head, absence of stemmata, presence of a sensorial field on antennomere III, and elongated and broadened mandibles of pupae and adults are autapomorphies of Prostomidae. The placement of Prostomis within Tenebrionoidea is suggested by the posteriorly diverging gula with well developed gular ridges and the anterior position of the posterior tentorial arms. Affinities of Prostomidae with the pythid-pyrochroid-lineage is supported by the pad-like structure of the maxillary articulatory area, the abdominal tergite IX extending to the ventral side of the segment, and the strongly pronounced prognathous condition. Presence of a distinct molar tooth is a derived feature shared by Prostomidae, Pythidae, Pyrochroidae, Inopeplidae and Othniidae. A thorax narrower than the head and the abdomen, and a plate-like abdominal segment IX, which articulates with segment VIII, are possible synapomorphies of Prostomidae, Boridae, Mycteridae and Pyrochroidae. The strongly flattened, prognathous head and the strongly flattened body of larvae of Prostomidae are correlated with their habits of boring in wood of decaying logs.