Two Littoral Species of Dicranomyia (Idioglochina) (Diptera: Limoniidae) from Japan: a New Species and Transfer of D. monostromia with Notes on Ecology

Abstract

The marine-associated crane fly subgenus Idioglochina Alexander, 1921 of the genus Dicranomyia Stephens, 1829 comprises coastal species whose immature stages are associated with shoreline habitats, but its diversity and ecology in Japan remain insufficiently documented. Here, we report two littoral species of Dicranomyia (Idioglochina) from Japan based on specimens collected from rocky shores in Mie and Shizuoka Prefectures. We describe D. (I.) nagisa sp. nov. from Yawatano, Izu Peninsula, Shizuoka. The new species is distinguished from congeners by the combination of an unmarked wing, an open discal medial cell caused by atrophy of crossvein m-m, and a uniformly sclerotized male inner gonostylus with a blunt, non-pointed apex. Adults of the new species were observed walking on dry seaweed and rocks in the upper splash zone, suggesting a narrow supralittoral habitat preference. We also transfer D. (Dicranomyia) monostromia (Tokunaga, 1930) to the subgenus Idioglochina based on its serrate antennal flagellomeres and coastal ecology, supporting a previously suggested but unadopted subgeneric placement. Field observations indicate that adults of D. (I.) monostromia are abundant along rocky shores from late March to early April and that females search for oviposition sites not only on Monostroma Thuret (green algae) but also in other intertidal microhabitats. DNA barcodes based on partial cytochrome c oxidase subunit I and 16S rRNA sequences are provided for both species. These findings improve the taxonomy of Japanese marine crane flies and highlight the ecological specialization of shoreline insects in intertidal environments.