Factors affecting the proportion of soldiers in eusocial bamboo aphid,Pseudoregma bambucicola, colonies

The proportion (percentage to all individuals) of soldier-type first-instar larvae in colonies of the eusocial aphid, Pseudoregma bambucicola, was measured at bamboo stands in Kagoshima Prefecture, Japan, in relation to colony size, percentages of adults and alatae, host conditions and syrphid natural enemies. A significantly positive correlation was found between the soldier proportion and colony size in all 3 months. Multiple regression analysis showed that the colony size and the proportion of alatae had highly significant partial regressions to the soldier proportion. Length of bamboo shoots on which colonies were observed showed a positive correlation to the soldier proportion, but this correlation was not supported by multiple regression analysis. The number of syrphid larvae living in colonies showed a negative, but insignificant, correlation to the proportion of soldiers.