The larva of Thyreus Abbottii possesses a peculiar interest to the Entomologist, as it is the only species of which the sex is supposed to be indicated by the coloration. Frequent reference to this is found in works of different authors, and nowhere have I seen any doubt expressed about the validity of the distinguishing markings between ♂ and ♀ (vide Harris' Ent. Correspondence, p. 284; N. Y. State Museum Report, p. 114; Can. Entomologist, 1874, p. 146).