Abstract
Under a long day condition a linear relation between temperature and developmental velocity in both species, Agrotis ipsilon and Agrotis fucosa, was observed at 15∼30°C in the egg stage and at 20∼30°C in the larval stage. The calculated threshold of development and the thermal constant of the egg and larval stages in the two species was 11.3°C, 56.5 day degrees and 5.6°C, 387.3 day degrees in A. ipsilon and 11.0°C, 78.7 day degrees and 4.2°C, 589.0 day degrees in A. fucosa respectively. The threshold of development in both stages was hardly different in the two species, but there is a remarkable difference in the developmental duration between these two species, especially with increasing temperature. The larval development was more or less retarded under short day condition in A. fucosa, whereas in A. ipsilon no such tendency was observable not only under short but also long day condition. From the results it may be suggested that in A. fucosa the larval diapause was induced by photoperiodic condition.
