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.
Males of the giant water bug, Lethocerus deyrolli, care for egg masses on vegetation above the water surface. They supply the developing eggs with water and guard them against predators. In the present study, mechanisms by which paternal care is extended were found. Males were found situated just below the water on the natal substrate (usually a stick), and the first instar nymphs were aggregated around the substrate. When disturbed, the males showed aggressive behavior, threatening the intruder with their forelegs. Nymphs up to 12 h old did not attack the offered sibling nymphs or anuran larvae, which are common prey in the field. The 24 h-old nymphs attacked both prey animals; however, they preferred anuran larvae. Cannibalistic behavior in the nymphs was well developed 72 h after hatching, when the nymphs had already dispersed from the natal substrate. The suppression of sibling cannibalism in younger nymphs would promote the maintenance of tight nymphal aggregations and consequently extend male care in this predatory species.
To examine the effects of tillage practices on spider assemblages in rice paddy fields, we investigated the abundance and biomass of spiders in untilled and tilled paddy fields over three cropping seasons (from 1999 to 2001). In total, we collected 6,829 spiders, consisting of 13 species in seven families. The family Lycosidae was the most abundant, followed by Tetragnathidae, Linyphiidae, and Salticidae. Spider abundance and biomass were greater in untilled than in tilled paddies during each cropping season. Although we detected no significant effect of tillage on spider abundance, we did observe a significant effect of tillage on spider biomass in 2000 and 2001. No differences were found in the abundance and biomass of tetragnathid and linyphiid spiders during the cropping season. In contrast, the abundance and biomass of lycosid or salticid spiders tended to be larger in untilled paddies than in tilled paddies, especially later in the cropping season.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.