588 



In a few cases, as in Glaucopteryx ccesiata and Rheumaptera liiguhrata, 

 the Pacific-coasI specimens resemble the European examples more than those 

 from the At [antic coast. 



It would seem as if these differences were almost wholly due to climatic 

 causes. The climate of the Rocky Mountains and of Vancouver's Island is 

 much wanner than that of Northern New England, the highlands of 

 British America, and Labrador. The mean annual temperature of Victoria, 

 Vancouver's Island, is 48° F.; that of New York City being 52° F., while 

 that of Denver, Colo., is 48° F., and of the Rocky Mountains from 44° to 

 40° F.; that of Northern New England being from 44° to 40° F. ; 

 the White Mountains and the Adirondacks and the region north of the 

 Great Lakes being 40° F., while that of Labrador is from 32° to 30° 

 F. The annual rain-fall of Victoria, Vancouver's Island, is 3ti inches; at 

 the mouth of the Columbia River, it is 80 inches ; while that of Saint John's, 

 Newfoundland, is 63 inches (this is probably the same as that of the southern 

 and eastern coast of Labrador). The rain-fall of Denver, Colo., is 12 inches, 

 while, of course, that of the more elevated portions of the Rocky Mountains 

 is probably nearly 20, though no data are given in the Smithsonian charts. 

 The rain-fall of the Rocky Mountain region is colored in Guyot's map the 

 same as that of the Ural and Altai Mountains. The annual rain-fall of Fort 

 Dalles, Oreg., is 20 inches, while that of Walla- Walla, a little farther east- 

 ward, is 16 inches. On the other hand, that of Nertchinsk, in the Altai 

 Mountains, is 17 inches, while that of Peking is 24 inches ; so that the annual 

 rain-fall of the elevated plateaus of Northeastern Asia and Colorado is nearly 

 the same. Again, the annual rain-fall of the Alps, on their southern slopes, 

 is from 60 to 90 inches ; here we have conditions quite similar to those of 

 the Cascade range in Oregon. 



These meteorological facts seem to explain the corresponding zoo-geo- 

 graphical data given above. The warmer and more humid Pacific slopes of 

 America cause a more luxurious growth, a greater development of the periph- 

 eral parts of the body, and slight changes in coloration. The climatic con- 

 ditions of the Rocky Mountains and Alps being more alike than those of the 

 White Mountains and Alps, we have certain identical features in the variation 

 of the alpine species of moths of those two ranges of mountains, which are 

 not found in comparing White Mountain and Labrador individuals with those 

 from the Alps of Europe. 



It will be seen from the facts we have presented that the moths probably 



