Ecological Knowledge of Endangered Species Libelloides ramburi (M'Lachlan, 1875) in Kanagawa Prefecture, Japan

Abstract

Libelloides ramburi is an endangered species whose distribution in Kanagawa Prefecture is currently limited to a corner of the northern part of the prefecture. In this study, we report the results of the ecological survey conducted in 2020 and 2021. We newly observed that this species rested on dead herbal stems such as Japanese pampas grass in the nocturnal habitat. In addition to the preference for resting places of the L. ramburi (i.e., Japanese pampas grass in the early stage, rice grass in the latter half), we also found that the specie has the preference for the height of the resting position. In 2021, we marked 174 adults of L. ramburi for individual identification, of which 6 % were recaptured. The result suggests that adult members in the populations interchange rather frequently. The number of days to survive was as follows: male: 34 days, female: 24 days. The ratio of males was high in the early stage, but it was remarkably decreased in the later stage. Other new ecological knowledge are 1) Two species of spiders were recorded as predators of this species, 2) The average number of eggs in a mass was 60.4, 3) The majority of spawning targets were dead stems of alien plants, Solidago canadensis var. scabra (74 % of the total spawning targets).