FIELD AND FOREST. 51 



The Alpine insect fauna of America should be as but a fragment of 

 that which survived the geological changes which occured at the close 

 of the Tertiary epoch. Although the mountain genera and species 

 are nearly all represented in the Arctic fauna by the same species or 

 their analogues, yet the number inhabiting the latter region is greatly 

 in excess of the former, as would naturaly be supposed in view of the 

 general migration of the Alpine fauna which must have occured when 

 the great ice field receeded to the North. 



The moths of the Pacific Coast are generally larger than those of 

 the Rocky Mountains, and almost invariably larger than the same spe- 

 cies from New England and Labrador. The western species also show 

 such a marked increase in the length of wing that it may be regarded 

 as a law of variation similar to that which obtains with the North 

 American birds. Dr. A. S. Packard, Jr., regards this variation of 

 peripheral parts to be due to the more gonial climate and greater rain 

 fall of the western coast. I would like to suggest the possibility of 

 this variation being in some degree due to the prevalence of high winds 

 which have operated to produce greater developement of the wings as 

 a natural result of greater habitual exertion in combating them. And 

 also to the acquisition of nomodic habits, rendered necessary in a 

 comparatively barren region where vegetation is not as exurberant as 

 in more civilized localities which have been under cultivation for a 

 long time. 



Calopteiius sprefiis, the swarming grasshopper, singularly confirms 

 this law. This insect having been accustomed to sustain a flight equal 

 to twenty degrees of latitude, has consequently developed more pow- 

 erful wings than the same species in the eastern states, which differs in 

 no respects from the western insect, except in its habit of local resi- 

 dence and its shorter wings. 



As regards variation of color, I believe that species from a cold cli- 

 mate or where there is an unusual absence of sunshine will be charac- 

 terised by the predominence of sombre hued types, or will present a 

 bleached appearance when compared with specimens from a warmer 

 climate. In the Arctic regions the short summers seem poorly adap- 

 ted to the developement of vivid colors, and we accordingly find few 

 of the Coleoptera, known to occur then, which are remarable for bright 

 colors. The same fact is noticeable in the Coleoptera obtained from 

 the western mountains above the timber line. However, more com- 



