Adaptive advantages of matriphagy in the foliage spider, Chiracanthium japonicum (Araneae : Clubionidae)

Young of the Japanese foliage spider, Chiracanthium japonicum, show matriph agy, whereby they consume their own mothers before dispersal. By removing m others in the laboratory, I examined the importance of this sacrificial hab it for offspring survival and dispersal behavior. Spiderlings that cannibal ized their mothers gained weight more than threefold and dispersed from the ir breeding nests after molting into the third instar. The third-instar spi derlings had relatively longer legs than the previous instars and appeared to be more adapted to a solitary hunting life style. On the other hand, mos t spiderlings separated from their mothers could not molt into the third in star and dispersed significantly earlier than those with matriphagy. Furthe rmore, the lack of matriphagy decreased the survival rate of predispersal s piderlings. These results showed that matriphagy of C. japonicum has a grea t advantage in allowing offspring to disperse at a more developed and activ e instar.