Morphology and biology of Homoplectra gracilis Nozaki, 2019 in a headwater stream in Yata Hills, Japan

Homoplectra Ross, 1938 (Hydropsychidae) comprises 24 species. Knowledge of the immature stages of species in this genus is quite poor. This study aimed to describe for the first time morphology of Homoplectra gracilis Nozaki, 2019 larvae, found in small headwater streams flowing throughout 'Satoyama', a unique and important ecosystem in Japan, and clarify its biology. Morphological observations showed that the larva of this species is unique among known Japanese species in having a small median triangular process on the anterior margin of the head. Final instar larvae were found throughout the year, whereas the second instar larvae were observed during July and November. The species retreated using various kinds of substrates; on/between leaves, plants roots, and under stones. Analysis of digestive tracts showed predominantly detritus in their diet along with remains of invertebrates. The larvae appeared to withstand drought which occur in the streams.