Diabrotica is a large New World genus of galerucine chrysomelids that includes several pests. The catalog of Wilcox (1972) lists 338 species in three groups; the virgifera and fucata groups include pests. The genus has never been revised systematically, but the synopsis by Wilcox (1965) provides a systematic context for this genus in North America north of Mexico. Those species of Diabrotica recognized as pests are listed in Table 1. Where agriculture is poorly developed, some pests probably have gone unrecognized because the damaging stage is frequently subterranean (e.g., Krysan and Branson, 1983). This chapter summarizes the distributions, briefly describes Diabrotica biology, and presents aids to the recognition of pest species and the determination of the sex of pupal and adult forms.