Abstract
Autographa gamma responds to a short chilling (hardening) in every stage including the pupal one with increased cold-hardiness, while the closely related species, A. nigrisigna has little response (Kaneko, 1996). The nuclear spin-lattice relaxation time (T1) of water and alkyl groups in the pupae of these two species was measured to detect any change in these substances due to hardening. The T1 values of the alkyl group in A. gamma but not of water were significantly decreased by chilling, indicating possible increase in unsaturated bonds in fatty substances. In A. nigrisigna, no change due to chilling was detected in the T1 values of both the water and alkyl group.
