The purpose and scope of this work is to set forth as clearly as possible the taxonomic characters of the species of aphids recorded up to 1950, on both native and introduced plants in the state of Colorado and adjacent territory belonging to the same biotic areas as contained in Colorado. The region herein treated comprises the whole series of life zones beginning with the Arctic-alpine which is inhabited by practically no aphids, to, but not including, the Lower Sonoran or desert zone. Geographically, the region comprises the Southern Rocky Mountains, the Wasatch and Uintah Mountains, the Jemez and Sangre de Cristo Ranges and adjacent plains. Politically, the region comprises the entire states of Colorado and Utah, southern Wyoming, southeastern and southern central Idaho and northern New Mexico.

-- From the introduction, page 1