94 



Sierra Club Bulletin, 



do not form a complete flat color layer on the wings. This 

 curious and wholly unusual character and disposition of the 

 scales in the Parnassians is associated with several other 

 structural aberrances which are hardly of a nature to interest 

 the general reader, but which add to the interest that these 

 strange butterflies have for students of insects. 



I should make an end of this paper, and yet I have said 

 nothing about the life of the larvae, or caterpillars, of the 

 mountain butterflies. There is indeed not much to be said 

 about them, for not much is known. Of Papilio indra, for ex- 

 ample, the eggs, caterpillars and chrysalids are still wholly 

 unknown. And this is true of some of the others. But of 

 others, still, some little is known of the immature life, and it 

 all agrees in revealing a high tolerance of low temperatures on 

 the part of the caterpillars. There is indeed little doubt that 

 most of them can be frozen and then thawed out with perfect 

 safety. The eggs are laid on dried grasses or on the proper 

 food plant, and the whole immature life is gone through with 

 ve^"y swiftly. Just as some mosquitoes of desert regions are 

 able to condense their larval Hfe into one or two days and their 

 pupal life into a few hours, the whole keeping pace with the 

 short existence of a swiftly drying pool formed by one of the 

 rare desert rains, so the butterflies of the mountain-tops have 

 had their life-history adapted to the short alpine summer sea- 

 son. With the oncoming of this season when the sun burns 

 hot and melting, through the thin atmosphere, on the great 

 snow-banks, small grasses and flowers spring up swiftly by the 

 wet edges of the snow and along the tiny rivulets that run 

 away from it. On these low green plants the caterpillars feed 

 voraciously and grow rapidly. The chrysalids are formed, 

 either oji the ground or attached to plant stems, nearby, and 

 the issuing butterflies quickly expand their wings, have a few 

 sips of nectar, and a few dancing flights over the rocks and 

 fragrant flower patches, then mate, lay their eggs and die. A 

 week must be a fair old age for most of the summit butterflies ; 

 a fortnight is octogenarianism, and any longer is the miracle 

 of Methuselah. 



