Abstract
In the Osaka population, the critical photoperiod for the induction of diapause did not vary with temperatures ranging between 20°C and 30°C, and the sensitive period ranged from the latter half of the egg-stage to the 2nd-instar larval stage immediately before the diapause. Leucoma candida (STAUDINGER) had been recorded only in northern Japan until it was discovered in Kobe in 1957. Field survey conducts in the period 1971-1978 showed that this species was already distributed throughout the Kinki district and parts of the Chugoku and Chubu districts. The photoperiodic response did not show any clinal variation. In the Kinki and adjacent areas the critical photoperiods of the bivoltine Osaka, Kurasiki, Okayama and Himeji populations were similar to that of the univoltine Matsumoto population. In northern Japan, the Akita population showed a univoltine type of photoperiodic response, while the farther northern Sapporo population showed a critical photoperiod of about 15.5hr, only 1hr longer than in the southern populations. It was inferred that the southern populations were derived from a population accidentally introduced from southern Korea into Kobe or Osaka.
