The biochemical mechanism of cold-hardiness in overwintering larva of Dend-rolimus spectabilis Butler(Lepidoptera: Lasiocampidae)

One of the most striking characteristics of overwintering insects is their capacity to accumulate high concentrations of low-molecular-weight polyols and sugars, and that can greatly affect the cold-hardiness of overwintering insects. Dendrolimus spectabilis is one of the most destructive pests attacking pine tree, it overwinters as larva in the cold winter in Shandong Province. In the present study, experiments were carried out to examine the relationship between the content of bio chemical substances and cold-hardiness of overwintering larva of D. spectabilis.Results showed that the content of low-molecular-weight carbohydrates in the larval haemolymph in January was about 3.8 times of that in October, especially the content of glucose, trehalose and sorbitol increased about 908%, 184%, and 644%, respectively, while the glocogen decreased about 56.5%.Compared with the larva before winter period, the content of threonine , serine, glutamicnine, alanine, cystine in the overwintering larva increased about 493.75%,433.70%,474.15%,21.45% and 47.08%, respectively. However,the content of glycine, asparticacid, methionine, leucine, phenylalanine, tyrosine, histidine,arginine,proline decreased remarkably. During the over-wintering period, the content of fat in over-wintering larva decreased, but the protein increased, and the diagrams of glyprotein electrophor-esis analysis showed that the content of glycoprotein increased about 200% than that in the larva before overwinter. The results in this paper indicated that the main antifreezes in the overwintering larva of D. spectabilis included low-molecular weight carbohydrates (sorbitol, trehalose, glucose)-glycoprotein-amino acid (alanine, threonine etc.).