2005 Volume 68 Issue 5 Pages 575-578
Damselfly Coenagrion terue living in Sawada Springs in Hitachi Seaside Park is a rare population as its habitation is near the shore while most other populations of this species are distributed in high lands. Office of Hitachi Seaside Park has been trying to conserve this population by placing ponds and repairing existing ponds in this area. We thought that providing optimal food supply for the naiads, the larval stage of the damselfly, was one of the important means to maintain this population and the strength of sunlight was also an important environmental factor for nursery ponds for the naiads. In this study, to clarify which were actual species of prey for naiads and the relationship between food supply and the degree of sunlight, we examined gut contents of naiads, meiobenthos as prey in ponds, the strength of sunlight and the density of naiads. The main prey of naiads were benthic Arthropoda. Body widths of prey were limited to 100-500μ m and the maximum body widths of prey were proportional to the head widths of naiads. Not only the density of naiads, but also the number of species and the density of prey tended to be lower in dark ponds than those in bright ponds.
