Through the process of evolutionary trial and error gall insects now feed at the proper rate so that they do not kill all of the developing plant tissue. Thus the gall insect benefits by obtaining reliable food and shelter, while the plant is neither harmed or benefited. There are many types of plant galls and each insect produces a totally unique, characteristically-shaped gall. The variable physical appearance of the many galls is due to the type of insect causing the gall and the part of the plant affected. Galls may occur on just about any part of a plant - roots, stems, twigs and branches, leaf stems, leaves, buds and flowers.
Some galls have commercial value.
They are used in the manufacture of inks, dyes, tannic acid, medications and food. Insects are not always able to defend themselves, and so many of them have developed ways for blending into their surroundings. Some insects hide in plain sight, their bodies resembling non- living or inedible objects such as bark, thorns, buds, twigs, leaves, or bird droppings. Other insects, such as the stick insects are shaped like twigs or leaves. The dead-leaf butterfly of India is also another example of this type of protective coloration and camouflage.