Members of the family Aphididae were among the first insects to attract attention in this country, and consequently to be investigated by entomologists. From the time of Harris and Fitch, until the present, a large portion of the writings of economic entomologists have dealt with them. During all this time, although more or less complete lists of the described species have been published, there has not appeared a catalogue. It is believed that, as a result of the confusion coming from the lack of bibliographical references, and the consequent difficulty of finding what has been written concerning any certain species, that the study of these most important and interesting insects has been neglected in recent times. The object of the present work is, in some measure, to bring together what is known about the North American species of Aphididae, as a basis for future investigation. Writers have been describing new species, establishing synonyms, adding points in the life-history, and suggesting methods of destroying, until a veritable chaos has reigned. That the best method of advancing the interests of a department of knowledge, at such a stage, is in making a complete summary of all that has been done, certainly requires no proof.