Abstract
Leiobunum japanense (Müller 1914) is a species of harvestman endemic to Japan, which is divided into two subspecies based on the external morphology of apophyses on trochanters of legs and palpi: L. japanense japanense (Müller 1914) and L. japanense japonicum (Suzuki 1940). Their distributional boundaries had remained unclear due to the lack of collection records. Therefore, we investigated the distribution of these subspecies through field research and compared their morphological characters. Field sampling revealed that L. j. japanense is distributed in the eastern and central Gifu Prefecture, whereas L. j. japonicum is distributed in a narrow region in the westernmost part of Gifu Prefecture. At the two sampling sites where the two subspecies meet, individuals with characteristics resembling one of the two subspecies-like were dominant on either bank of a river, suggesting that the river might have separated the two subspecies, though specimens showing intermediate conditions were also found in a population.
