CORRELATIVE INFLUENCE OF GUT APPEARANCE, WATER-CONTENT AND THERMAL HYSTERESIS ON WHOLE-BODY SUPERCOOLING POINT OF ADULT BARK BEETLES, IPS ACUMINATUS GY11

Adults of the bark beetle Ips acuminatus rely upon supercooling for ov erwintering success. In preparation for winter, individuals stop feedi ng, and increase their supercooling capacity, Isolated alimentary cana ls froze within the temperature range of intact adults, and the agents responsible for nucleation were of a proteinaceous nature, Enhanced s upercooling from -12 to -17 degrees C could be attributed to the evacu ation of residual food from the gut and a reduction in water content, while a further shift to -20 degrees C was closely correlated with the level of thermal hysteresis. The principle carbohydrate present durin g autumn, the disaccharide trehalose, increased from 10 mM at the end of August to 90 mM in November, and seemed to account for a decrease i n supercooling points of approximately 1.5 degrees C.