Notation of primary setae and pores on larvae of Dytiscinae (Coleoptera: Dytiscidae), with phylogenetic considerations

Abstract

An analysis of the primary setae and pores of first instars of 13 species of Dytiscinae was performed to deduce the ancestral system of primary setae and pores of the head capsule, head appendages, legs, last abdominal segment and urogomphus. One hundred and thirty-one setae, 69 pores and three setal groups have been assigned to the ground-plan pattern of the dytiscine larva, 27 setae and 20 pores on the head capsule; 30 setae, 25 pores and three setal groups on the cephalic appendages; 51 setae and 18 pores on the legs; 15 setae and three pores on the last abdominal segment; and eight setae and three pores on the urogomphus. A hypothesis of the phylogeny of the tribes of Dytiscinae is presented on a cladistic analysis of first instar chaetotaxy characters conducted using the program TNT. All tribes of Dytiscinae were included with larger tribes represented by multiple genera. Our concept of the subfamily Dytiscinae as defined on the basis of first instar chaetotaxy was found separated into three distinct clades: (1) Cybistrini, (2) Dytiscini + Hyderodini, and (3) Aubehydrini + Hydaticini + Eretini + Aciliini. The proposed relationships of the tribes of Dytiscinae are ((Cybistrini + (Hyderodini + Dytiscini)) + (Aubehydrini + (Hydaticini + (Eretini + Aciliini)))). Characters useful for phylogenetic analysis of the subfamily are described and illustrated.