Larval morphology and phylogenetic relationships of Bunites distigma (Brulle) (Coleoptera : Dytiscidae : Colymbetinae : Colymbetini)

摘要

Bunites Spangler has been the only member of the tribe Colymbetini for which the larva has been unknown. The first-instar larva of Bunites distigma (Brulle) is described and figured for the first time. Detailed morphometric and chaetotaxic analyses are provided. A phylogenetic analysis based on 41 first-instar larval characters, including members of six genera of Colymbetini, Supports the hypothesis of a derived condition of Bunites within this tribe. Monophyly of Bunites + Rhantus Dejean (s. lat.) (minus Rhantus orbignyi Balke) +Neoscutopterus J. Balfour-Browne + Meladema Laporte is suggested by four synapomorphies: an elongate and hair-like seta FE5 on both meso-and metafemur, and the presence of additional anteroventral setac on tibia and tarsus. The clade Bunites + Neoscutopterus + Meladema is supported by three synapomorphies: the presence of additional setae on the frontoclypeus, dorsal surface of parietal, and urogomphi. Six other character states might also support this group. The clade Bunites + Meladema is well supported by four synapomorphies: the presence of additional setac on the lateromedial portion of frontoclypeus, ventral surface of parietal, anterodistal margin of prementum, and anterodorsal surface of tibia. A derived condition of Bunites within the Colymbetini is suggested by two autapomorphies: the presence of one additional seta on the coxa, and additional dorsal pores on the eighth abdominal segment.