THE CANADIAN ENTOMOLOGIST. 215 



the propagation of animals, and assisted the development of the civiliza- 

 tion of man. In America we have evidence of the former existence of 

 human societies along the Ohio River, and to whatever branch of historical 

 studies we may betake ourselves, the topography of the country must 

 supply the foundations and become fixed in our minds. It is the scaffold- 

 ing upon which is displayed the picture of animated Nature. After the 

 physical features, the prevailing winds, the amount of rainfall, the average 

 warmth must be observed. Early in my studies I became interested in 

 the migrations of the Lepidoptera in North America. A yearly zoological 

 wave sets in from the tropics and carries upon its crest numbers of light- 

 winged Moths, which eventually range up our entire coast, and are found 

 in Maine in the autumn. Tlie summer, that pulse of the year, the length 

 of whose recurring beat is at once the measure of the time elapsed since 

 the culmination of the last ice period, gives us a prevailing northward 

 direction for the winds that sweep the North American continent. They 

 offer aerial paths along which numbers of feathery winged moths are hur- 

 ried. They distinctly aid the dispersal of the Cotton Moth, for instance, 

 and on the coast of Georgia it comes earlier or later as the south wind has 

 blown fitfully or steadily. We have wind visitors on our shores during 

 the whole season, some of which become citizens for a lime by breeding 

 intermittently within our territory. 



All natural barriers succeed to some extent in producing more or 

 less local variation in flora and fauna, and local variation ends, in connec- 

 tion with the climate, in producing distinct species. The species of moths 

 inhabiting islands, or confined between mountain chains, often show dis- 

 tinctive features in color, size and markings. From what I have seen I 

 think that Thy at ir a Pudens^'^ found on Anticosti, has become grayer, the 

 pink spots less vivid than on the main land; the darkening by mixing of 

 color, noticeable in Polar species, has here taken place. Many other 

 instances occur to me in writing, but it is sufficient here to refer to local 

 variation as affording an interesting part of the study of Lepidoptera. 

 After a certain phase of variation has been attained it seems probable 

 that interbreeding stops, and that, were the original form introduced, it 

 would continue breeding side by side and without intermingling with the 



* This variety is worthy of a distinct name, and in my second Check List of N. 

 Am. Noct. (MSS.) I have called it A)iticosticnsis, The moth is grayer, more hoary, 

 the pink color has faded. Mr. Wm. Couper has taken this form on the island. 



