Abstract: The daily and seasonal dynamic changes of carbonhydrate and lipid contents in hemolymph of the 5th instar larvae of pine caterpillar (D.punctatus), and the metabolic effects of a pyrethroid (Deltamethrin) and an organophosphorous insecticide (Trichlorfon) were studied. The results for the normal (untreated) larvae were as follows:(1) The changes of the total hemolymph carbonhydrate contents are shown in following orders: Active summer larvaeActive larvae before hibernation Active larvae after hibernationHibernatant larvae, their respective concentration being 65.5, 33.1, 32.8 and 30.0mg/ml.(2) The changes of total hemolymph lipid content have been arranged in the following order: Active larvae before hibcrnationActive summer larvaeActive larvae after hibernationHibernatant larvae, their concentra. tion being 67.3, 63.2,48.8 and 10.7 mg/100 ml respectively. The results also showed that the daily changes of the hemolymph carbonhydrate contents of untreated larvae were negatively correlated with those of lipid contents.In addition, it was found that the effects of deltamethrin and trichlorfon to the concentration changes in hemolymph carbonhydrate and lipid were quite different. Deltamethrin would cause the elevation in hemolymph carbon-hydrate and the depletion of blood lipid during most of the experimental period. The trichlorfon-treated larvae, on the other hand, exhibited a decrease in the hemolymph carbonhydrate contents. Also, the hemolymph lipid contents would be elevated with the onset of hyperactivity and depleted then after. Finally, the best time for controlling massonpine caterpiller by using insecticides and the mechanisms of insecticide-induced changes hemolymph carbonhydrate and lipid metabolism were discussed in this paper.