Environment, plant, and gall-inducing insect genotypes are key factors in determining the morphogenesis of galls. However, the exact roles of these factors have not been clarified. We used anatomical and histochemical methods to evaluate the determining factors in the final structure of galls induced by Calophya mammifex on leaves of Schinus polygama (Cav.) Cabrera under the Mediterranean climate conditions of southern Chile. Also, we compared mature galls with those induced by the congeneric Calophya rubra on the same host plant. Calophya mammifex develops a univoltine life cycle and a diapause period in the Mediterranean climate conditions of southern Chile. Morphogenetic and histochemical leaf patterns were altered by C. mammifex feeding activity. For the first time, two specialized tissue compartments, a nutritive-like tissue and a common storage tissue, are reported for Calophyidae-induced galls in the Mediterranean region of southern Chile. Galls induced by C. mammifex and C. rubra have sufficient anatomical and histochemical alterations to be diagnosed as complex structures, whose distinction in vascular system differentiation implies structural constraints imposed by host plant organs.