38 THE BUTTERFLIES OF THE WEST COAST 



were everywhere, doing nothing, "just flying about and feeding 

 on flowers," and the residents were said to be apprehensive of the 

 "army worm," but I never heard that the army really did appear. 

 This migration, then, was over a known distance of about twenty 

 degrees of latitude, or, say, 1,400 miles. The rate of flight I esti- 

 mated at eight miles an hour, which would require one hundred 

 and seventy-five hours' actual flight for the journey ; but as they 

 could not fly more than eight hours a day, seventeen days' travel 

 would be required from Mexico across the United States to Can- 

 ada. It is quite possible, however, that the Mexican butterflies 

 may, many of them, have stopped in the States, and others from 

 the States have taken their places in the grand march for the 

 north. 



§ 39. Stranded Butterflies. 



This term is by some writers applied to such species as inhabit 

 the tops of high mountains and not the intervening plains or val- 

 leys ; they are said to be stranded, being confined to those peaks, 

 and presumably not being able to cross over the warmer valleys. 

 For instance, Semidea is said to be "stranded" on the tops of the 

 White Mountains of New England ; Gigas may, therefore, be 

 said to be stranded on the bare rock knobs of Vancouver Island, 

 and Ivallda, and Indra, on the alpine peaks of the Sierra Nevada, 

 and so on, because they probably do not pass from one to another 

 of such heights, and do not live in the intervening valleys ; having 

 become inhabitants of these inhospitable localities during some 

 previous and colder climatic era, they are now apparently on the 

 ' verge of extinction, if the climate should, perchance, become yet 

 more moderate than it now is. 



This opinion I do not share. Such butterflies live on these high, 

 inhospitable localities simply from choice. If they see but one 

 sunny hour during the week of fog and rain and gale, that one 

 hour is sufficient; they do not feed on flowers, therefore why 

 should they care for them? Their sole business is to mate and 

 to oviposit their eggs on the fine alpine grasses that grow in the 

 crevices of the rocks, and they then die, having lived their ap- 

 pointed lives in the places they like best. Reverse the case : the 

 butterfly which lives in the warm valleys only, is it "stranded" 

 there, and is it liable to extinction when a cold cycle occurs ? Oh, 

 no. Neither is the alpine butterfly stranded. The cold, barren 



