Abstract: During 1955 and 1956, the pine barkbeetle, Cryphalus fulvus Niijima, seriously injured pine trees in the Nanking District. Only at Tung-san-chow, more than thirty thousands of Pine trees had been killed. Its life history has been observed and descri. pted as follows:1. It has five generations a year in Nanking.2. In the first generation: eggls period, five days; larval period, 34 days; pupal period, 4 days; and females adults, after imerged for 7-10 days, begin to lay eggs.3. The serious damaging period is from August to October.4. Adults prefer trees which has been injured by pine caterpillars or piles of logs. on the trunk, it prefers the bark smooth,and withinl. thick.5. Its outbreak related with the following factors: the amount of rainfall from July to October ina year management of the forest and the injuries of the pine trees by the pine caterpillars.