Inconsistencies in larval habits of the Nearctic Calocalpe population have been known to lepidopterists of eastern North America for over a decade, at least since the publication of The Lepidoptera of Nantucket and Martha's Vineyard Islands, Massachusetts by Dr. Frank Morton Jones and Mr. Charles P. Kimball (Nantucket Maria Mitchell Assoc., IV, 1943). In writing of the occurrence of undulata on Martha's Vineyard, Dr. Jones mentioned “solitary larvae, identified by breedings, occasional on Azalea”. Since only the common gregarious larvae on cherry were known up to that time and always considered as representing an American variant of undulata, the report of a solitary larva on a totally different food plant sounded interesting. This was drawn to my attention by Mr. Laurence R. Rupert of Sardinia, N.Y., who did so much to inspire my interest in Lepidoptera in earlier years. On a collecting trip with him to Martha's Vineyard in 1947, one of the things sought for was the Calocalpe mentioned by Dr. Jones. We did not find any, but since that time Dr. J. McDunnough and I on a number of occasions have bred specimens from solitary larvae on Rhodora at Halifax. Since Rhodora and Azalea are closely related, I assume this to be the same as the Martha's Vineyard species. Dr. McDunnough bred one from a larvae on Spiraea, the specimen emerging just in time to be mentioned in this paper. On another occasion I bred one from a single larva on willow, undoubtedly also the same species, and this provided the first clue to its relationship with the Palaearctic willow-feeding undulata.