DIFFERENCES IN COLD-HARDINESS BETWEEN SIL VER-Y MOTH, AUTOGRAPHA-GAMMA (L) AND ASIATIC COMMON LOOPER, AUTOGRAPHA-NIGRISIGNA (WALKER)

The cold-hardiness of the Silver-Y moth, Autographa gamma, at the egg, larval and pupal stage was compared with that of the Asiatic Common L ooper, A. nigrisigna. In each stage, nearly all individuals died at ch illing (0 degrees C, 100% RH) for 10 to 30 days without hardening (10 degrees C for 1 day and then 5 degrees C for 5 days). However, if hard ened, more individuals survived chilling for more days in both species . This effect was most remarkable in A. gamma. Hardened third-instar l arvae of A. gamma survived chilling for 120 days at a rate of 1.4%. By contrast, no individuals of hardened A. nigrisigna survived chilling for 90 days.