The individual distribution is less aggregated in C. melanurum; the mate locating tactics of the male are of the "searching” type, while in C. nipponicum the tactics are of the ”sit-and-wait” type, and the individual distribution is more aggregated. In C. nipponicum, the male groups hold their position near the waterside and the female groups gather outside the male groups, thus increasing the probability for the two sexes to encounter each other. C. melanurum travels further in its day-to-day movements, but there is a strong tendency for both species to stay at or return to their original sites.