1998 Volume 33 Issue 2 Pages 281-288
The distribution of the great mormon butterfly, Papilio memnon L., has been expanding to northeastern areas in the Kinki district in western Japan. To investigate the relationship between the phenomenon and characteristics of diapause of this species, the photoperiodic response of 4 Japanese populations including the subtropical and northernmost ones was examined. The critical photoperiod for inducing diapause at 20°C was 12 h 30 min in a subtropical population in Naze City (28°23′N), and about 13 h in temperate populations in Kagoshima (31°36′N), Wakayama (34°11′N), and Mino (34°54′N) Cities. Latitudinal variation was not found in diapause intensity (94-111 days) among the 3 temperate populations. However, diapause incidence at 13.5L-l0.5D, which is slightly longer than the critical photoperiod, increased with latitude of the locality, and the deepest diapause was observed in some individuals in the Mino population. Nevertheless, the differences in critical photoperiod and diapause intensity among populations was smaller than that among broods in each population. As it appears to be difficult to explain the recent northward invasion of this species only by this slight change in diapause trait, the influence of climatic warming on the phenomenon is also discussed.