Anuran-dependent predation by the giant water bug, Lethocerus deyrollei (Hemiptera: Belostomatidae), in rice fields of Japan

We examined the seasonal dietary patterns of the endangered giant water bug, Lethocerus deyrollei, in rice fields located at Sayo, Hyogo Prefecture, central Japan. The results showed that L. deyrollei underwent a shift in its major food item from breeding adults of Hyla japonica in spring (May and June) to newly metamorphosed juveniles of Rana nigromaculata in summer (July to September). Dietary shifts were shown to correspond with a seasonal fluctuation in the availability of anurans in the rice fields. Although adults of R. nigromaculata were relatively abundant throughout the active season they were infrequently exploited by L. deyrollei, possibly because of the difficulty in handling these large-sized frogs. Therefore, seasonal partitioning of the rice-field habitat by small-sized frogs, adult H. japonica and juvenile R. nigromaculata, would enable L. deyrollei to forage in the rice fields during the extensive active period. From these results, we suggest that the conservation of frog populations is very important for the preservation of this endangered insect and for the maintenance of biodiversity within these rice-field ecosystems.