The notes and descriptions that follow arise from material submitted for identification from various sources over the past few years. Doubtless much still remains to be discovered in this genus, and a general revision would be premature at this time. The number of striking new species is surprising: every new collection seems to yield one or two more. Despite the great superficial variation in the genus, the genitalia are very uniform. The main structural variation externally is in the mouth-parts, the labial palpi varying considerably in length and the tongue tending towards obsolescence in many species. There seems to be considerable variation in development of the tongue even in single species, and I doubt if this can form the basis of subdivision of the genus. Most or all of the old-world species and some new-world ones have been wrongly referred to this genus; however, I shall leave the disposition of these extraneous elements to a future paper.