Our knowledge of the life history of Polites mystic Scud, is limited to Scudder's (1889) description of the early stages and to a few supplementary notes on these stages by Dethier (1938). <br /><br />In addition to describing the chrysalis of this species, hitherto unknown, and the last larval instar, which has been incompletely described by Scudder, notes on the younger instars have been included in this paper. It is felt that these additional notes will be of value if keys to Hesperiid larvae are ever to materialize, because any key must take into consideration minute changes in detail, especially, since larvae of the different species of this family so closely resemble each other. On the other hand, there is marked variation in the duration of the different stages, particularly the later ones and all data are important. For this reason supplemental data are given for the early stages. Also, hibernation in this species has been studied for the first time.