Journal of Citrus Pathology

With SEM, we studied external midgut surfaces of all potato psyllid instars, and, additionally with SEM and TEM, the anterior alimentary system of adults. The ontogenetically earliest point of Lso detection was in the 3^rd instar, then in consecutively greater percentages of 4^th and 5^th instars, then in a lower percentage of teneral and mature adults. Two age-based patterns of proliferation were identified in the oral region of mature adults- streaming, in which Lso were confined to passageways, and diffuse, in which Lso occurred inside of, and around, cells of mouthpart components, muscles and epidermis.