Previous work on community structure of the invertebrate fauna of Japanese wetlands indicates the presence of intraguild predation between the heteropterans Laccotrephes japonensis (Nepidae) and Kirkaldyia deyrolli (Belostomatidae). We designed a series of experiments to understand the biotic interactions of several species of sympatric heteroptera and their shared prey. Adult Laccotrephes japonensis (Nepidae), first-instar nymph of Kirkaldyia (=Lethocerus) deyrolli (Belostomatidae), Hyla japonica tadpole, and fourth-instar nymph of Appasus japonicus (Belostomatidae) have been shown to be intraguild predator, intraguild prey, common prey, and prey of L. japonensis, respectively. To further understand the factors affecting prey preference by L. japonensis, we also examined the comparison of swimming speed in the three prey animals (K. deyrolli first-instar nymph, A. japonicus fourth-instar nymph, and H. japonica tadpole), and effects of prey animals on weight gain of L. japonensis adult. Despite there being no significant difference in weight gain or swimming speed of the three prey species, L. japonensis exhibited a strong preference for the 1st-instar nymph of K. deyrolli. We suggested that this may be evidence for one of elimination of a potential competitor, K. deyrolli, by L. japonensis through intraguild predation
