Effects of gall volume on survival and fecundity of gall‐making aphids Adelges japonicus (Homoptera: Adelgidae)

Summary The number of larvae reaching maturity within the gall of Adelges japonicus was positively related to gall volume, and the relationship between the number of mature larvae and gall volume did not change with different densities of colonized larvae. The population changes in the bud galls of A. japonicus were surveyed by collecting the galls, which did not suffer predation or parasitism within the galls, from young artificial plantations of Picea jezoensis over two years. In the year when the density of colonized larvae was high, they suffered a 42% mortality within the galls, whereas mortality was nearly zero in the low density year. The numbers of larvae per gall were positively correlated with gall volume. The regression lines of the number of colonized larvae on gall volume did not differ significantly in the regression coefficients between the two years, whereas the intercept was significantly higher in the year when the density of colonized larvae was higher. However, different within‐gall mortality nullified this difference, and the regression lines of the number of mature larvae on gall volume had no significant difference both in the regression coefficients and the intercepts. This suggests that the number of mature larvae per gall was limited by available resources within the gall which were positively related to gall volume. In 25% of the galls in which mature larvae inhabited, the space within the galls were completely filled by the larvae, indicating that space was one of the limiting resources. Gall volume also affected the number of adults that emerged from the gall and the potential number of their progeny.