Eleven orders are included, one per chapter. Each chapter begins with general remarks about the order. An overview of a family is made, and then the genera in that family, and species within each genus are described. Whenever there are several families, genera or species, keys to identification are given. The greatest details are found at the species levels.
Distribution is described, and maps are given to illustrate current ranges.
Usual habitats are briefly noted. Habits, including daily and seasonal cycles, movements, special abilities, etc., are detailed. Food and feeding, when known, are discussed. Reproduction and development, including mating behavior, litter sizes, growth of the young, etc., are described. Population characteristics, such as relative abundance, territory size, and population density, are noted.