Recent publications on gall formation induced on the leaves of dicotyledonous flowering plants by eriophyoid mites (Eriophyoidea) and representatives of four insect orders (Diptera,
Hemiptera, Hymenoptera, Lepidoptera) are analyzed. Cellular and molecular level data on the
stimuli that induce and sustain the development of both mite and insect galls, the expression of
host plant genes during gallogenesis, and the effects of these galling arthropods on photosynthesis
are considered. A hypothesis is proposed for the relationship between the size of galls and the
volume of secretions injected by a parasite. Multistep, varying patterns of plant gene expression
and accompanying histo-morphological changes in the transformed gall tissues are apparent. The
main obstacle to better elucidating the nature of the induction of gallogenesis is the impossibility
of collecting a sufficient amount of saliva for analysis, which is especially important in the case of
microscopic eriophyoids. The use of modern omics technologies at the organismal level has revealed
a spectrum of genetic mechanisms of gall formation at the molecular level but has not yet answered
the questions regarding the nature of gall-inducing agents and the features of events occurring in
plant cells at the very beginning of gall growth.