DESCRIPTION OF THE LARVAE OF ELEVEN NEARCTIC SPECIES OFHYGROTUSSTEPHENS (COLEOPTERA: DYTISCIDAE: HYDROPORINAE) WITH AN ANALYSIS OF THEIR PHYLETIC RELATIONSHIPS

Publisher Website
Google Scholar
Abstract
A systematic analysis of larvae of 11 Nearctic species ofHygrotusStephens was undertaken. The larvae are described and characterized; a key for their discrimination and illustrations of structural features of representatives of first- and third-instar larvae are provided. Many structural features, especially detailed variations in the chaetotaxy of cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi, were found to be useful for systematic and phylogenetic comparisons. Based on 21 larval characters, a cladistic analysis of the species studied was developed. A sister-group relationship betweenH.laccophilinus(LeConte) and the remaining available species is suggested. The less derived species, i.e. those without natatory setae on the legs, appear phylogenetically more closely related to the larvae ofHydroporus s.str.Hygrotus masculinus(Crotch) is the most derived species of the genus and, for many characters, seems more closely related to Hyphydrini. According to larval morphology, it is hypothesized that the genusHygrotusdiverged posteriorly to the genusHydroporusClairville.