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 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 species known). Advice is provided on collection, preservation, slide-mounting, vouchering, and labelling of specimens, fully illustrated with color photographs, diagrams and drawings. Pest species are presented in two informal groups of families, the 'primitive' Archaeococcids followed by the more 'advanced' Neococcids, covered in phylogenetic order. Each family is illustrated and diagnosed based on features of live and slide-mounted specimens, with information on numbers of genera and species, main hosts, distribution, and biology. For the important pest species, coverage includes information on the morphology of live and slide-mounted specimens, common names, principal synonyms, geographical distribution, plant hosts, plant damage and economic impact, reproductive biology, dispersal, and management strategies including biological, cultural and chemical control, sterile insect techniques, regulatory control, early warning systems and field monitoring. An additional complete list of scale insect pests worldwide is provided, comprising 642 species in 28 scale insect families (about 8% of the 8396 species of living scales known), with information on plant hosts, geographical distribution and validation sources. Beneficial uses of scale insects as sources of red dyes, natural resins and waxes, as agents for invasive weed control. The importance of their honeydew to bees for making honey, and as a food source to other animals, are included. Academic researchers, students, entomologists, pest management officials in agribusiness or government including plant quarantine identifiers, extensionists, farmers, field scientists and ecologists will all benefit from this book.