A Newly Distribution Recorded Population of the Caddisfly Hydatophylax nigrovittatus in Nagano Prefecture and Its Emergence Period

摘要

The caddisflies of the species Hydatophylax nigrovittatus (McLachlan, 1872) are distributed sporadically ana in extremely isolated areas, in the Japanese Archipelago. In addition, this species has been registered as a Red List species, i.e., in category "DD (data deficient)' in the Nagano Prefecture. We report a newly found habitat at an extremely high density in Nagano Prefecture in 2014. We collected some pupae of these cadaisflies from the population, and we tried to obtain data with respect to the timing of their emergence by incubating them in the laboratory. The result of our breeding attempts for the 50 individuals collected was that 44 adults achieved successful emergence. The sex ratio of the emerged adults was d ：=27:17 {i.e., ca. 6 ： 4). It is believed that in terms of the competition between males to acquire females that the earlier emerging males had a competitive advantage and were better prepared for the emergence of the females.