Larval morphology of the tribe Matini (Coleoptera: Dytiscidae, Colymbetinae): descriptions of Batrachomatus daemeli, Matus bicarinatus, and Allomatus nannup and phylogenetic relationships

Abstract

AbstractDescriptions are presented of larval instars of three species of the colymbetine tribe Matini Zimmermann (Coleoptera: Dytiscidae), Batrachomatus daemeli (Sharp), Matus bicarinatus (Say), and Allomatus nannup Watts, including a chaetotaxic and porotaxic analysis of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi. A parsimony analysis based on 32 informative larval characteristics was conducted with the computer program NONA. Members of the Matini are postulated to share a monophyletic origin based on (i) seta TR2 articulated anteroventroproximally on the trochanter; (ii) seta TR5 elongate on the metatrochanter; (iii) seta TA1 elongate and inserted proximally on the tarsus; (iv) antenomere III with a hole-like ventroapical spinula; (v) prementum with the primary setae LA2, LA3, LA4, LA5, and LA8 spine-like and elongate; (vi) presence of secondary setae on the cephalic appendages; and (vii) presence of additional primary setae on the last abdominal segment. A clade Matini + Colymbetini is postulated based on (i) metafemoral seta FE5; (ii) metafemoral seta FE6; (iii) seta TI6 on tibia, all elongate and hair-like; (iv) one-segmented urogomphus; (v) presence of an occipital suture in first instar; (vi) galea elongate; (vii) presence of natatory setae on legs; and (viii) presence of secondary setae on the urogomphus.