Galls, regardless of the host plant organ, are strong sinks of nutrients. This physiological phenomenon provides gall tissues with essential building components and nutrients necessary for the proper development of both the gall and the gall-inducing organism. In the galls induced by many species of insects, mites, or nematodes, the main storage substances are carbohydrates, especially starch, which demands enzymatic activity related to carbohydrate metabolism, such as the UDP-glucose pyrophosphorylase whose reduced activity in galls compared with leaf cells may be manifested by increased starch content. In plants, as well as in galls, starch is usually the form of stored energy, and as a non-transport carbohydrate, starch must be synthesized within gall tissues. However, there is currently limited knowledge about the activity of enzymes responsible for starch synthesis in galls. The distribution of amyloplasts in gall tissues usually increases centripetally, with the last layer of cells adjacent to the gall chamber usually free of them. In many cases, as the insect develops, the chamber expands, and the developing gall-inducing organism benefits from successive layers of starch-rich tissue layers. It is not fully understood whether starch is initially hydrolyzed to simple sugars, which are then absorbed by the larvae, or if chewing insects may metabolize starch in their digestive tract. Nevertheless, insect amylolytic enzymes have not been detected in gall-inducing insects, yet. Also, the difference in carbohydrate metabolism in gall-inducing insects and their inquilines, which directly benefit from the starch-rich layers of galls, is another issue demanding attention.