The species described here, Anagyrus beneficians, sp. n., can easily be distinguished from the great majority of species by the colour of the flagellum, which is completely black. Another good diagnostic character that will aid in the identification of this species is the arrangement, in six longitudinal rows, of the coarse dark setae on the frontovertex.

Relatively few species of Anagyrus have been described which have the flagellum wholly black. Among these species are : nigricans, Perkins, fusciventris, Gir., nigriflagellum, Gir., subnigricornis, Ishii, punctifrons, Timb., marquesanus, Timb., orbitalis, Timb., and longicornis, Mercet. Specimens of only one of these species are available for study, namely A. fusciventris, Gir. The species described as new is very much like A. fusciventris in all the major structural characters. Both belong to a group of species characterised by a very short ovipositor. These two species differ in some of their minor characters. In A. fusciventris, the tips of the forewings appear hyaline or silvery, due to a narrow band of refractive cilia at the apex of the blade. In A. beneficians, the forewings are uniformly ciliated. The three species described by Timberlake, from the Marquesas Islands, punctifrons, marquesanus, and orbitalis, have the head, thorax, and abdomen black, in colour unlike A. beneficians. Likewise, the species described by Girault, from Australia, A. nigriflagellum, differs in coloration, the head and thorax are orange yellow. In A. nigricans, the apex of the pedicel is reddish, while in the new species it is wholly black. In A. subnigricornis, the scape is marked with white at the base as well as near the apex, and the frontovertex at the anterior ocellus is as wide or slightly wider than the head width, in which respects it is unlike A. beneficians. In A. longicornis, Mercet, the abdomen is truncate at the apex, the pedicel reddish, and the head and thorax yellow ; all of which separate this species from A. beneficians. In this brief resumé it is possible that some species have been overlooked which have the flagellum completely black. However, the conditions under which Anagyrus beneficians originally existed and its subsequent introduction into Kenya Colony strongly indicate that the species has not been described previously.