FACTORS AFFECTING THE PROPORTION OF SOLDIERS IN EUSOCIAL BAMBOO APHID, PSEUDOREGMA-BAMBUCICOLA, COLONIES

The proportion (percentage to all individuals) of soldier-type first-i nstar larvae in colonies of the eusocial aphid, Pseudoregma bambucicol a, was measured at bamboo stands in Kagoshima Prefecture, Japan, in re lation to colony size, percentages of adults and alatae, host conditio ns and syrphid natural enemies, A significantly positive correlation w as found between the soldier propertion and colony size in all 3 month s. Multiple regression analysis showed that the colony size and the pr oportion of alatae had highly significant partial regressions to the s oldier proportion. Length of bamboo shoots on which colonies were obse rved showed a positive correlation to the soldier proportion, but this correlation was not supported by multiple regression analysis. The nu mber of syrphid larvae living in colonies showed a negative, but insig nificant, correlation to the proportion of soldiers.