We are informed that "Stegomyia calopus" has been adopted by the Public Health and Marine-Hospital Service and by the Bureau of Entomology, Department of Agriculture, as the official name of the yellow fever mosquito. In the matter of nomenclature this insect has undergone many vicissitudes. Among the names by which it has been known, Culex fasciatus, Culex calopus and Stegomyia fasciata are the most familiar. The mosquito since recognized as responsible for the spread of yellow fever was originally classified as a culex and received over a century ago the title Culex fasciatus, a name previously bestowed on an insect not identical with the one in question. The term Culex calopus was proposed somewhat later, and with the recent transference of this mosquito to the genus Stegomyia the name Stegomyia calopus resulted.