Cecidogenetic Behavior of some gall-inducing thrips, psyllids, coccids, and gall midges, and morphogenesis of their galls

Several plant species, belonging to diverse and unrelated families of Angiospemae respond to insect action by developing a gall. Development of a gall is a complex phenomenon that involves subtle alterations initiated at critical and specific points of time during plant differentiation. Galls are truly modified plant tissues; however, galls arise as a sequel to insect attack only, ensuring a suite of adaptations to the inducing insect. Natural selection seems to favor those insects that are able to introduce a perturbation in the plant's growth and developmental process. Unlike the free-living insects, gall-inducing insects display an imperative demand of a particular plant species to complete their life-cycles; such a relationship includes specialized feeding and reproductive behaviors, high levels of specificity to host plants, and contribution to the dynamics of the evolution of the gall-inducing guild. Against this background, this review summarizes and analyzes morphogenesis of some galls induced by thrips, psyllids, coccids, and gall midges in the context of the behavior of the inducing agents, studied mostly from subtropical peninsular India. The review concludes with a comparative synthesis of the available information on insect-induced galls in general, and in the particular context of galls induced by thrips, psyllids, coccids, and gall midges from other biogeographical regions, and the biologies of those insects.