著者

北野 忠 畠山 類

出版者

東海大学

雑誌

東海大学紀要. 教養学部 (ISSN:03892018)

巻号頁・発行日

vol.36, pp.235-244, 2006-03-30

被引用文献数

1

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The population changes of giant water bugs and seasonal changes in their suitable habitats were investigated in paddy fields in Inasa-Cho, Shizuoka Prefecture, Japan from July 1997 to December 1998 to obtain a basic ecological understanding of this species. Our results showed them to appear for only a limited period between May and August. The investigation also revealed that the sites investigated were breeding grounds for the species and that the period between June and August was the growing season for the larvae. During the period in which the species was observed, the water temperature and the population density of tadpoles were higher, and a water depth of approximately 20cm was maintained due to water management for rice production. On the other hand, no giant water bugs were seen from September to April of the next year. During this period, the water temperature and tadpole population density were lower and the water was shallower, at less than 10cm. Therefore, in the sites investigated, the presence of giant water bugs changed with the schedule of the water management of the paddy field. In addition, the growing period of the larvae was consistent with the period in which the water temperature and the population density of tadpoles were higher. Next, the relationship between the population of giant water bugs and the population density of tadpoles, which are prey species for the water bugs, was investigated in June 1999. Paddy fields with higher population densities of tadpoles showed greater populations of giant water bugs. It therefore appears that the propagation of the giant water bug depends on the population densities of frogs.