Relationship between distribution of dragonfly species and environmental factors in small irrigation ponds in Hokuda-cho, Hyogo Prefecture

Dragonfly species were surveyed in 23 small irrigation ponds in Hokudan-cho, Hyogo Prefectre in order to detect environmental factors influencing dragonfly distribution. Thirty-two species and 1066 individuals were observed from May to October 2001. The number of dragonfly species had no significant relation with water body area of irrigation ponds. Twenty-three ponds were classified to three types by TWINSPAN (Two-way Indicator Species Analysis). The result showed that neighboring woodlots and frequency of cutting glass around pond influenced the component of dragonfly species. Cutting glass is one of the important maintenances of irrigation ponds. It was suggested that the disturbance by traditional farm works such as cutting glass plays an important role to maintain dragonfly species richness on this area.