From the Editors. 173

Pattee, P.A., C.J. Schroeder, and M.L. Stahl. Erythromycin-sensitive mutations of transposon Tn551 in Staphylococcus aureus. 175

Thibodeau, G.A. and P.A. Hartman. Selective medium for the isolation of streptococci from clinical samples. 181

Shipp, J.L. and W.A. Rowley. Electrophoretic studies of Culex pipiens, Culex restuans, and Culex salinarius (Diptera: Culcidae). 185

Pohl, R.W. New records of Mesoamerican grasses. 191

Hinz, P.N. and G.B. Pitman. Analyzing data on insect response to pheromones: From a field study of the western pine beetle. 195

Devey, M.E. and W.A. Russell. valuation of recurrent selection for stalk quality in a a maize cultivar and effects on other agronomic traits. 207

Arjmand, O. and R.H. Shaw. Irrigation potential on Iowa soils of low water-holding capacity as determined by computer simulation. 221

Foley, D.C. Mechanical properties of Zea mays stems. 235

George, J.R. and K.E. Hall. Herbage quality of three warm-season grasses with nitrogen fertilization. 247

Wray, P.H. and D.R. Prestemon Assessment of street trees in Iowa's small communities. 261

Book Review. 269