Greenbug,Schizaphis graminum(Rondani), clones were collected in fields from eight localities in the central United States. Two clones collected from sorghum,Sorghum bicolor(L.) Moench, and one clone obtained from the Agronomy Greenhouse, North Dakota State University, Fargo, N. Dak. (initially isolated on barley in 1968) were identified as biotype C. Six other clones collected from sorghum fields were identified as biotype E. All clones were cultured in the laboratory on barley,Hordeum vulgareL.; oats,Avena sativaL.; ‘Piper’ sudangrass,Sorghum sudanensisBailey; and Kentucky bluegrass,Poa pratensisL., as standard diets. All clones were tested for fecundity during 10-d experiments in two chambers with automatically controlled 14:10 (L:D) photoperiod at 24 ± 1°C and 25% relative humidity. Fecundity of biotypes C and E was determined on the same host plants and on corn,Zea maysL., susceptible sorghum, biotype-C-resistant ‘IS-809’ sorghum, and biotype-C-resistant ‘Amigo’ wheat. Clones of the same biotype from different localities did not show differences in fecundity on the same host plants after being previously cultured on the same host plants. Biotype C showed greater fecundity on Kentucky bluegrass and on ‘Piper’ sudangrass after culturing on barley. Biotype E had greater fecundity on oat and ‘Piper’ sudangrass after culturing on barley. On corn, greenbugs did not survive longer than a week. All greenbugs grew slowly on ‘Amigo’ wheat and ‘IS-809’ sorghum. Greenbugs had higher fecundity on ‘IS-809’ sorghum than on ‘Amigo’ wheat.