Abstract
Daytime collections of adult chironomids resting on the shore and those floating on the water surface were carried out on February 8,1995,on a day in the coldest winter season of a year under the atmospheric temperature of about 8℃. A total of 76 adult male specimens were collected, and 60 among them were Biwatendipes motoharui Tokunaga, 3 were Biwatendipes biwamosaicus sp. nov., 5 were Hydrobaenus biwaquartus Sasa et Kawai, 1 was Hydrobaenus biwagrandis sp. nov., 1 was Orthocladius biwaniger Sasa et Kawai, 3 were Smittia aterrima (Meigen), 3 were Smittia nudipennis (Goetghebuer). The new species Biwatendipes biwamosaicus sp. nov. is quite unusual in the structure, the apical scales of tibiae and the hypopygium of males are characteristic of Biwatendipes, but the structure of head is similar to that of females, and wings are extremely wide.
