The mealybug genus Ferrisia Fullaway is revised to include 18 species, based on morphological and molecular data. We distinguish the widespread pest species F. virgata (Cockerell) from morphologically similar species and provide a revised description and illustration for the adult female of F. virgata. We resurrect Dactylopius dasylirii Cockerell stat. rev. from synonymy with Dactylopius virgatus Cockerell as Ferrisia dasylirii (Cockerell) and apply this name to many North American and Caribbean populations previously recognised as F. virgata; F. dasylirii is the most difficult to distinguish morphologically from F. virgata and exhibits morphological and molecular variation among some populations. We designate a lectotype for D. dasylirii Cockerell. Eight new species of Ferrisia are described and illustrated based on the adult female, and named as Ferrisia colombiana sp. n., F. cristinae sp. n., F. ecuadorensis sp. n., F. kondoi sp. n., F. milleri sp. n., F. pitcairnia sp. n., F. uzinuri sp. n. and F. williamsi sp. n. The relationships of five of these new species and five named species are discussed in relation to a previously published phylogenetic tree that was based on nucleotide sequence data. Taxonomically informative morphological features (such as the size, shape and position of discoidal pores associated with the dorsal enlarged tubular ducts and the ventral oral-collar tubular ducts), identified for each of the genetic groups (clades) on the tree, are used to help to diagnose the species. We also describe and illustrate the adult female of a form of F. gilli Gullan, found on Magnolia and some other host plants, that has numerous clusters of small ventral oral-collar ducts on the body margins. For seven named species-F. claviseta (Lobdell), F. malvastra (McDaniel), F. meridionalis Williams, F. multiformis Granara de Willink, F. quaintancii (Tinsley), F. setosa (Lobdell) and F. terani Williams & Granara de Willink-we provide revised illustrations of the adult females as well as diagnostic morphological notes and information on distribution and host plants. We also recognise Eurycoccus copallinae Ferris as a junior synonym (syn. n.) of Dactylopius quaintancii Tinsley (now F. quaintancii) and designate a lectotype for E. copallinae. We include photographs of the live appearance of the adult females of six Ferrisia species and also a key to all known species of Ferrisia based on the morphology of the adult females. We transfer the species currently known as Ferrisia floridana (Ferris) to a new monotypic genus, Pseudoferrisia gen. n., as Pseudoferrisia floridana (Ferris) comb. n., and provide a description of the genus and its type species (Ferrisiana floridana Ferris), as well as a new illustration of the adult female.