1. To elucidate the climatic adaptation of the house spider, Achaearanea tepidariorum, the photoperiodic response regulating diapause and the overwintering stage were compared between the 'temperate' Hirosaki and the 'subtropical' Okinawa strains. 2. Both strains could enter diapause in the nymphal and imaginal stages and photoperiod was a primary factor inducing it. In each strain, the critical photoperiod for diapause induction did not differ between nymphal and imaginal stages. There was, however, about 3h difference in the critical photoperiod between the two strains. It was longer in the temperate strain than in the subtropical strain. 3. The nymphal diapausing stadia also differed geographically; it was highly variable in the temperate strain, but was fixed at the final nymphal instar in the subtropical strain. In spite of the local difference in the diapausing stadia, all nymphal stadia and adults were found during winter in the field at both Hirosaki and Okinawa. 4. These observations suggest that the adaptive significance of diapause in the subtropical strain is to control the timing of reproduction, rather than to enhance the winter survival of the diapausing individual itself.
TANAKA, K
PHOTOPERIODIC CONTROL OF DIAPAUSE AND CLIMATIC ADAPTATION OF THE HOUSE SPIDER, ACHAEARANEA-TEPIDARIORUM (ARANEAE, THERIDIIDAE)
Functional Ecology