Taxonomical and biological notes on Tokunaga-yusurika akamusi (Tokunaga), with description of immature stages (Diptera, Chironomidae)

Abstract

A new genus, Tokunagayusurika, is created in the subfamily Orthocladiinae, with Orthocladius akamusi (Tokunaga, 1938) as a monotypic member. This species is quite unique both in morphology and biology as a chironomid. The body size is much larger than other members of the subfamily, and is almost as large as the giant midge, Chironomus plumosus (L.). The larvae are blood red in color, and are found in the bottom mud of eutrophicated lakes. The adults emerge once a year in late autumn. The structure of male genitalia, especially the shape of the style, is highly complicated and does not fit to any of the known genera. The adults are also unusual in that they lack in the comb on the apex of hind tibia. Morphological characters of pupae and larvae are newly described. This species is considered as to be playing a significant role in fixing and removing organic nutrients from eutrophicated lakes, but causes a serious nuisance during the season of its emergence.