Coleoptera, Diptera, Neuroptera, and less frequently in other insect orders and in ticks (Clausen, 1940). Aphycus. Host records for Ap•hycus refer almost exclusively to coccids or to chalcidoid parasites of coccids. Exceptions include two records from the Psyllidae. One of these concerns Aphycus (Metaphycus) psyllidis (Compere) which was found parasitizing the nymphs of the potato psyllid, Paratrioza cockerelli (Sulc) in California. Cercobelus. The species C. jugaeus Walker has been recorded once as a parasite of the psyllid Psyllopsis fraxinicola (Forster) in Scotland. Other host records for the genus have not been found. Cheiloneurus. The insect hosts of this genus are principally primary parasites of soft scales and other Homoptera. Two psyllid species have also been recorded as hosts, but it is probable that the Cheiloneurus were secondary parasites in these instances. Emcurtus. The hosts of this genus include the Psyllidae, Diptera, Lepidoptera, and Coleoptera, in addition to the soft scales which are the most common hosts. Metallon. This genus appears to be recorded only from the Psyllidae. Mirocerus. This genus was described (Ashmead, 1904) for a parasite reared from a psyllid. The original publication lists the type species as "peyelae." However, Gahan and Peck (1946) point out that this was a typographical error because the type, in the U.S. National Museum, is plainly labeled "psullae," Prionomitus. This genus appears to be parasitic principally on psyllids although it has also been recorded from Lecanium. Among the Psyllidae, Prionomitus mitraius is recorded from at least 13 species in four genera. Psyllaephagus. The 10 named species in this genus were all reared from the Psyllidae. In the present study, undescribed species of Psyllaephagus were reared from 10 species in seven genera of psyllids. Psylledontus. Three parasite species in the genus Psylledontus have been reared from three different species of psyllids in Ceylon, Japan, and New York, respectively. Psyllencyrtus. This monotypic genus was described in 1955 for a new parasite species reared from the psyllid, Syntomoza magna Kuwayama. EULOPHIDAE Aphelinus (Agonioneurus). Members of the genus Aphelinus are principally parasitic on aphids, but species have also been reported from Psyllidae, Coccidae, and even Coleophoridae. Aprostocetus. This genus is predominantly parasitic on gall midges, but one specie.s was reared from a psyllid and other records indicate Orthoptera, Lepidoptera, and Coleoptera may be hosts. Pteroptrix. The only host record found for this genus listed the psyllid Rhinocola eucalypti Mask. in New Zealand. Tetrastichus. The arthropod host list of the genus Tetrasiichus is very extensive. The major groups listed by Burks (1943) as being parasitized by Tetrastichus are Orthoptera, Odonota, 'I'hysanoptera, Homoptera, Neuroptera, Coleoptera, Lepidoptera, Diptera, Hymenoptera, and Araneae. At least eight species are now known to parasitize over 20 species of psyllids. Waterston (1922) thought the Tetrastichus species might be secon...