Metabolism and cold tolerance of Chinese white pine beetle Dendroctonus armandi (Coleoptera: Curculionidae: Scolytinae) during the overwintering period

Cold hardiness becomes a crucial strategy because temperature change often leads to fluctuations in insect abundance. The present study investigated the relationship between cold-tolerance ability in overwintering Chinese white pine beetle Dendroctonus armandi Tsai and Li larvae and physiological body indices aiming to determine the possible overwintering strategy from September 2013 to May 2014. Supercooling points (SCP) differed significantly across months, showing a precipitous drop in December 2013 and January 2014. The maximum monthly mean supercooling point was -1.7 +/- 0.4 degrees C (15 September 2013) and the minimum monthly mean was -7.5 +/- 0.2 degrees C (15 January 2014). The SCP tended to decrease as the ambient temperature decreased until January, before increasing until the end of the winter. Glycerol, sorbitol and trehalose contents showed a significant negative correlation with the SCP. The latter results indicate that the cold tolerance ability of the larvae is enhanced by exposure to 4.0 degrees C. Dendroctonus armandi larvae decreased their mortality at -8.0 degrees C after cold acclimation at 4.0 degrees C for 24 h.