Study of the larvae of Hydrotrupes palpalis sharp (Coleoptera : Adephaga, Dytiscidae) with implications for the phylogeny of the Colymbetinae

Description of structures of the three instars of Hydrotrupes palpalis Shar p are presented including detailed chaetotaxal and porotaxal analyses. Larv ae of Hydrotrupes Sharp are compared phylogenetically with those of seven g enera of the subfamily Colymbetinae. Hydrotrupes is hypothesized to be clos ely related phylogenetically with Agabus Leach and Ilybius Erichson based o n absence of the primary pore FRe, the more distal insertion of the primary sera CO7 on procoxa, and the presence of an additional spine on the maxill ary stipes. Larvae of Hydrotrupes are distinguished from all other colymbet ine genera by the remarkably modified and autapomorphic primary setae AB8 a nd AB14 found apico-laterally on abdomen segment 8, and the absence of a ma ndibular channel.