Bulletin No. I of the Colorado Biological Association
COLORADO, the State of lofty mountains, with its wonderful canons, gorges, and plateaux, a dry climate, and remarkable for its great mineral wealth and fossil remains, from its position in the Rocky Mountains affords a peculiarly interesting Fauna .. In the present memoir, it is intended to elucidate, as far as possible, a part of this, the hymenopterous fauna, describe such species as appear to be unknown to science, give notes, a list of the species occurring in the State, and show as much of their life-histories as is practicable.
Ashmead, William H., "On the Hymenoptera of Colorado; Descriptions of New Species, Notes, and a List of the Species Found in the State" (1890). An. Paper 74.