Morphological Diversity of Immature Scydmaeninae

Abstract

Larvae of ant-like stone beetles are exceptionally poorly known. Scydmaeninae comprises over 5000 species, but the immature stages have been described for less than 0.5% of them; the pupa has been illustrated for four species, and the first larval instar for only one species. In several tribes, larvae still remain unknown, and many descriptions are inaccurate or poorly illustrated. Chaetotaxic structures have been coded in only six species. Our knowledge of larval Scydmaeninae is so fragmentary that even for the largest, most common, and abundant genus, Euconnus Thomson (nearly 2500 nominal species!), the immature stages have never been adequately described. Known larvae of Scydmaeninae show a great diversity of body shapes and structures, more than expected within one subfamily of Staphylinidae. Known larvae of Eutheiini, Scydmaenini, Glandulariini, Mastigini, Clidicini, and Leptomastacini have a ten-segmented abdomen, whereas those of Cephenniini have only nine abdominal segments. Larvae of Eutheiini and Mastigitae are campodeiform, subcylindrical, or flattened, resembling those of other subfamilies of Staphylinidae. However, larvae of Scydmaenus s. str. are nearly onisciform, with demarcated laterotergites of thoracic segments, densely and asymmetrically covered with setae and microtrichia. Larvae of Glandulariini are also onisciform, but without demarcated laterotergites; they are sparsely setose and have nearly smooth cuticles. Larvae of some tribes have short, unsegmented urogomphs, whereas in others the urogomphs are absent. This chapter summarizes known data on the immature stages of Scydmaeninae, including their biology, indicating major problems and future directions.