Unlike simple feeding damage, a gall is not just a wound but a new plant structure produced under the influence of the inducing organism. When certain insects lay eggs in or feed on plant tissue, they release chemical signals—often through saliva or oviposition—that alter normal plant development. The plant responds by producing specialized tissues that provide both protection and nutrition for the developing larva. Galls occur in a wide variety of forms and on different plant organs, including leaves, stems, buds, and roots. On modern plants, some galls are small swellings or blister-like structures on leaves, while others are large and conspicuous. For example, on Distylium racemosum, large woody galls can resemble fruits in size and shape. Leaf galls vary greatly in shape (spherical, spindle-shaped, horn-like, pouch-like) and in their position on the leaf (along veins, on the margin, or on the lamina). Insects that induce galls include gall wasps (Cynipidae), gall midges (Cecidomyiidae), certain aphids, and some psyllids and moths. Many gall-inducing species are highly host-specific, often restricted to a single plant species or genus.