Primary setae and pores on the last abdominal segment and the urogomphi of larval Hydroporinae (Coleoptera: Adephaga: Dytiscidae), with notes on other dytiscid larvae

The first instar larvae of 24 North American species of Hydroporinae (Coleoptera: Dytiscidae), 6 species belonging to the three other dytiscid subfamilies, and 2 species each of Amphizoidae and Hygrobiidae are analyzed. The ancestral system of primary setae and pores on the last abdominal segment and the urogomphi of Hydroporinae larvae is deduced. Generic differences are discussed in a phylogenetic perspective. Laccornis Des Gozis is confirmed as one of the most primitive lineages in the Hydroporinae and we suggest that Hygrotus Stephens could be more evolved than the closely related genus Hydroporus Clairville. Informations on the primary chaetotaxy of other dytiscid larvae are also mentioned.