216 THE CANADIAN ENTOMOLOGIST. 



local form, until finally succumbing to the same influences. A good deal 

 of what we are now warranted in assuming, is merely reasonable con- 

 jecture in default of experiment, but more and more facts are becoming 

 known, all tending to throw light on the origin of species, and in this 

 progress' the study of Butterflies and Moths has proved of the greatest 

 assistance to naturalists and philosophers. 



As a special illustration of the study of the probable origin of our 

 North American fauna I may attempt a brief discussion of the genera 

 of our Hawk Moths, and present some tables of the different categories. 

 We have seen that there are three proximate sources for our fauna, i, 

 Descendants of an Arctic Tertiary fauna. This fauna was forced south- 

 ward and apart by the last Glacial Epoch, the species descending into 

 Central Asia, Southern Europe, and the American tropical and sub- 

 tropical region. This category includes species now identical in Europe 

 and America, and which have not been introduced by commerce in his- 

 torical times, while these latter form a distinct sub-category. 2, Descend- 

 ants of the North American Tertiary fauna, the members of which latter 

 occupied about the same limits that their descendants do to-day, probably 

 they ranged further to the North. 3, Descendants of an immigration from 

 the South. This stream is still of yearly occurrence. A colony, as we 

 have seen, has been planted in South Florida from the West Indies and 

 South America. Probably also, on the decline of the Ice Period, certain 

 species of South American origin settled permanently and became modi- 

 fied by their residence in the regained territory. This category includes 

 forms permanently domiciled and also such as visit us merely during the 

 summer and do not survive the winter. As belonging to the first category 

 in the Sphingidse we have the genus Hemaris, which in Europe has only 

 two species, but with us from 12 to 15. (The series Tenuis, Diffinis, 

 Marginalis and Axillaris, ranging from Canada to Texas, have probably 

 the same origin as the European Fucifonnis. And we have a distinct 

 sub-genus, Haetnorrhagia, which contains at least two distinct species, 

 Thysbe and Fuscicaudis. If we are to believe Mr. Hulst, U7iiformis is a 

 dimorphic form of Thysbe, differing, as I pointed out, by the evenness of 

 the inner edge of the terminal band of primaries. Now the typical series 

 of four species of Hemaris, above mentioned, differ from each other in 

 much the same way. In Tenuis the band is narrowest, tapering to anal 

 angle, being even inwardly and the usual red apical spot wanting, or at 



