The formation of galls - abnormal growths or swelling in a plant - may be induced by infection of the plant by bacteria or fungi, or attack from certain mites, nematodes or insects. This book provides comprehensive coverage of the biology of galls and their complex ecological etiology. The expert contributors address topics such as the effect of insect secretions on plant growth, the evolution and physiology of gall-inducing insects, patterns in gall development and induction, the role of nutritive cells, and many other key issues. This valuable work in cecidology will interest all biologists and botanists concerned with plant health, and entomologists working in the field of plant-insect relationships.