Book excerpt: Scale insects feed on plant juices and can easily be transported to new countries on live plants. They sometimes become invasive pests, costing billions of dollars in damage to crops worldwide annually, and farmers try to control them with toxic pesticides, risking environmental damage. Fortunately, scale insects are highly susceptible to control by natural enemies so biological control is possible. They have unique genetic systems, unusual metamorphosis, a broad spectrum of essential symbionts, and some are sources of commercial products like red dyes, shellac and wax. There is, therefore, wide interest in these unusual, destructive, beneficial, and abundant insects. The Encyclopedia of Scale Insect Pests is the most comprehensive work on worldwide scale insect pests, providing detailed coverage of the most important species (230 species in 26 families, 36% of the scale insect pest species known). Advice is provided on collection, preservation, slide-mounting, vouchering, and labelling of specimens, fully illustrated with colour photographs, diagrams and drawings.