LARVAL MORPHOLOGY OF 4 GENERA OF THE TRIBE HYPHYDRINI SHARP (COLEOPTERA, DYTISCIDAE, HYDROPORINAE) WITH AN ANALYSIS OF THEIR PHYLOGENETIC-RELATIONSHIPS

Description of structures of the larvae of 4 genera (Desmopachria Babi ngton, Hyphydrus Illiger, Microdytes Balfour-Browne, and Pachydrus Sha rp) of the tribe Hyphydrini Sharp is presented. The chaetotaxy and por otaxy of the cephalic capsule, head appendages, legs, last abdominal s egment, and urogomphi are discussed in detail. Within the subfamily Hy droporinae, the Hyphydrini are hypothesized to constitute a monophylet ic assemblage based on the following 7 synapomorphies: (1) absence of pore PAj, (2) epicranial plates meeting at the ventral midline, (3) ab sence of pore FRb, (4) medioventral position of seta FR6, (5) absence of pore ANh, (6) abdominal segment 6 sclerotized ventrally, and (7) pr oximal insertion of the primary seta UR8 on urogomphomere 2. It is pro posed that Pachydrus occupies a basal position within the Hyphydrini. A monophyletic origin is indicated for Macrodytes, Desmopachria, and H yphydrus based on the shared presence of an elongated prementum and a more proximal insertion of seta UR8 on urogomphomere 2. Desmopachria a nd Hyphydrus are related phylogenetically by the absence of lateral no tches on the frontoclypeus, the presence of at least 1 secondary seta on ventral surface of the siphon (3rd instar), and the short and spini form appearance of the primary seta UR5 in 1st instars.