GENERAL FEATURES 17 



In the distribution of butterflies as to latitude (and altitude has 

 nearly the same effect, as I have explained,) on the West Coast, 

 those species which are peculiarly indigenous to the immediate 

 coast are likely to be quite local and restricted in range, and 

 only those that are in a way continental or cosmopolitan are of 

 wide range. To this ruling there are exceptions ; among others, 

 Lini. Lorqidni is strictly a coast species, yet has a wide range to 

 the north and south, flying in the mountains of Western Mexico 

 and into Alaska I know not how far, suffering but very little dark- 

 ening of color, but being much smaller in the north. 



§4. Environment. 



In the determination of sub-species and variations, it is neces- 

 sary to call in all the side-lights that bear upon the matter: The 

 circumstances of habitat, altitude, and season should all be fully 

 considered. These are all carefully weighed in the determination 

 of birds and mammals, and they should be still more carefully 

 studied in the case of butterflies, because of the previous larval 

 stage of the latter. It appears to me that this aspect of the matter 

 has been largely ignored, perhaps because the writer who is dis- 

 cussing the matter but seldom has any knowledge whatever of the 

 matter, and apparently cares less about these preliminary stages 

 than their value demands. For environment has much influence 

 on all animals, and cannot safely be ignored. 



§ 5. Range of Butterflies. 



Range indicates the limits of flight of a species, in latitude or 

 altitude. Butterflies, more than birds, are dependent on plants 

 for one of the limiting causes of their range, for most species of 

 butterflies have but one larval food-plant, while birds can feed 

 anywhere, and can nest in any tree. The butterflies' double life 

 of the larva and the imago, both of which stages must usually be 

 fed, doubly limits the butterflies' range, as compared with that 

 of birds. 



Occasionally a butterfly is hardy and omnivorous enough to live 

 almost anywhere, as Pyramcis Cardni, and Vanessa Antiopa, 

 and consequently they are found over all the world, but such are 

 the exception. In part, also, some butterflies do not feed at all, 

 either on water or on the nectar of flowers, and these, as might be 

 surmised, are the most strictly limited in range of all the varieties 



