Larval morphology of the Palaearctic genera Deronectes Sharp and Scarodytes Gozis (Coleoptera: Dytiscidae: Hydroporinae), with implications for the phylogeny of the Deronectes-group of genera

Abstract

AbstractDescription of larval instars of Deronectes depressicollis Rosenhauer 1856, D. lareynii (Fair-maire 1858), D. latus (Stephens 1829), D. aubei (Mulsant 1843), and Scarodytes halensis (Fabricius 1787) is presented including a detailed chaetotaxic and porotaxic analysis of the cephalic capsule, head appendages, legs, last abdominal scgment and urogomphi. A phylogenetic analysis of 14 genera of the tribe Hydroporini, based on 22 larval characteristics was conducted with Hennig86. Three of the branches of the strict consensus tree have a statistical support greater than 60% according to the Parsimony Jackknifer. One of the supported clades is Antiporus Sharp + Nebrioporus Régimbart + Neonectes J. Balfour-Browne + Oreodytes Seidlitz + Stictotarsus Zimmermann + Scarodytes Gozis, of which the sister-group is the genus Deronectes Sharp. Consequently larval characters, in contrast to adult characters support the inclusion of Antiporus, Neonectes and Oreodytes in the Deronectes-group of genera. All members of this clade are characterized by: (i) presence of an occipital suture in first instar, (ii) presence of a constriction at level of occipital suture, (iii) absence of maxillary cardo, and (iv) insertion of the primary seta MX I on the maxillary stipes. Scarodytes is postulated to share a monophyletic origin with Nebrioporus, Stictotarsus, and Antiporus based on (i) the presence of natatory setae on femora, tibiae, and tarsi and (ii) the shape of the urogomphomere I which is more than 3.10 times longer than urogomphomere 2.