Abstract: The contents of some chemical materials in the needle of Pinus tabulaeformis fluctuate greatly with the seasons.The experiments demonstrate that the levels of B-pinene and phenolic chemicals ascend to their maximum in March and April,much higher than those in July and August.The needle gulped by hibernating and young larvae in March and April resulted in their higher mortality and longer life cycles.For the sake of avioding unfavorable nutrition and uneven weather in spring,the hibernating larvae practise the postdiapause transitional period through reducing feeding and keeping lower growth.They can neither recover normal development nor terminate their postdiapause transitional period until the resusciation of host plant.All mentioned above may be the suitable explanations for hibernating larvae to endure the long harsh period from the beginning of the larval climbing trees to their initiation of normal development in spring.