Ecological studies on the population of the pear leaf miner,Bucculatrix pyrivorella Kuroko (Lepidoptera : Lyonetiidae). III. Fecundity fluctuation from generation to generation within a year

The number of eggs laid per female of the pear leaf miner under laboratory conditions varied from generation to generation, but exhibited a tendency to increase from the overwintered generation to the 3rd generation. Change in potential fecundity from generation to generation, which had been examined by counting the number of eggs contained in the ovaries of a female, showed about the same tendency as the change in the actual number of eggs laid per female. Number of eggs in ovaries was significantly smaller in the overwintered generation than in the following 3 successive generations. The length of fore wings as an indicator of body size was significantly larger in the overwintered generation than in the other 3. Newly emerged females of overwintered generation possessed mature eggs in their ovarioles, but a slight progress in egg development in ovaries was observed by the 5th day after emergence. The fluctuation of population densities from generation to generation seemed to be influenced by the change in fecundity in each generation.