Life history of different giant water bug, Appasus japonicus (Belostomatidae: Heteroptera), populations throughout the Japanese Archipelago

As temperatures in the Japanese Archipelago vary, species widely distributed in Japan should have different active periods, ecologies, and life histories. Information on developmental zero and effective accumulated temperature is necessary to estimate life history. The giant water bug, Appasus japonicus, found in rice paddies, ponds, and other lentic waters, is distributed throughout Japan except for the Ryukyu Islands, and is a representative taxon in which the male cares for the eggs. In this study, we investigated the life history, including the length of the breeding season, of different A. japonicus populations from Hokkaido, Ibaraki, Hyogo, and Nagasaki. The developmental period, developmental zero, and effective accumulated temperature of the eggs and nymphs showed no significant differences among the populations. The life history for each population was estimated based on climate data. This showed that the Hokkaido population had a shorter and more extremely limited breeding season than the other populations. The estimated number of generations during one breeding season was approximately one in Hokkaido, two in Ibaraki and Hyogo, and three in Nagasaki. The estimated number of times males cared for eggs during the breeding season was less than one in Hokkaido, eight in Ibaraki and Hyogo, and twelve in Nagasaki. Although Belostomatidae may carry multiple egg masses during the breeding season, this study shows that the male of the Hokkaido population does not care for multiple egg masses.