An assemblage of 24 grasshopper species inhabited a mixed grass prairie site near Livermore, Colorado. Ten species were gomphocerines, 9 melanoplines, and 5 locustines; the gomphocerines represented ca. 80% of total density, melanoplines 15%, and locustines 5%. Grass feeders, gomphocerines and most locustines, made up 85% of total density. The dominant species was Ageneotettix deorum which contributed 52% of the grasshopper density in 1981 and 37% in 1982. The grasshopper population was at outbreak density both years, 60/m2 in 1981 and 36/m2 in 1982. The pasture had never been treated with insecticide or herbicide. The Shannon-Wiener index of ca. 2.00 indicated a high grasshopper diversity.