Larvae of Apatura metis hibernating in Hokkaido froze at -32℃ spontaneously, while they were frozen at -7℃ when ice-inoculated. Although the frozen larvae tolerated down to -19℃ for 24hrs, yet they avoided inoculative freezing by two ways: 1) to prevent water invasion onto ventral integument, through which ice-inoculation occurred, by lateral hairs and silken mat, 2) to choose hibernating site on east-northern surface of host tree trunk, where inoculation should hardly occur. The larvae accumulated glycerol in haemolymph to the amount of 6.5% of fresh body weight, together with 0.5% trehalose. For comparison, cold resistance in larvae of Sasakia charonda hibernating in litter layer was also studied. They showed no inoculation avoidance despite relatively weak ability of freezing resistance, and contained trehalose (1.4%) but no glycerol.
View full abstract