Abstract

Uniparental, sibling, and semi-species are defined and the taxonomic problems associated with them discussed, with special reference to parasitic Hymenoptera. It is emphasized that such species frequently are overlooked or ignored and considered to be so-called races or strains. Criteria are outlined concerning the recognition and naming of uniparental species of parasitic Hymenoptera. Such species are indicated to be much more common than realized and of considerable significance to biological control research. Likewise, sibling species of parasitic Hymenoptera are rather common and support is developed for their recognition and formal naming whenever possible. The importance of semi-species to biological control research and application is emphasized. Examples are presented relating to each of the taxonomic categories considered.