Morphology of immature stages of Helophorus (Gephelophorus) auriculatus (Coleoptera, Helophoridae)

The morphology of immature stages of Helophorus (Gephelophorus) auriculatus Sharp, 1884 is described. This is the first description of the larva and pupa of the subgenus Gephelophorus Sharp, 1915. We describe the morphology of the egg-case, all larval stages (first to third instar, including chaetotaxy of the head) and pupa. Morphological transformations between larval instars were examined. Head chaetotaxy was nearly identical between instars. Ventral teeth on the nasale, considered as a useful taxonomic character, were absent in the first instar but well developed in later instars. Chaetotaxy differed among the subgenera Gephelophorus, Helophorus and Lihelophorus in the length and shape of setae on head capsule and maxilla. Pupal morphology was similar to that of previously described pupae: H. (Helophorus) aquaticus (Linnaeus, 1758) and H. (Rhopalohelophorus) orientalis Motschulsky, 1860. A key to families of the Hydrophiloidea of Japan based on larval characters is provided.