ABSTRACT
The occurrence of facultative microorganisms in phloem-feeding insects, particularly aphids (Hemiptera, Aphidoidea), has been recognized for many years (see Buchner, 1965), but it is only recently that their phylogenetic position and biological function have been explored in detail. Undoubtedly, their newfound fame is largely a result of advances in molecular biology, particularly the ability to characterize unculturable microorganisms, but whole insect studies to manipulate the bacterial tenants have also played a role in assessing the contribution of the bacteria to insect biology.
