LIFE AT HIGH ALTITUDES HINGSTON 339 



ibis bill is a more strikino; instance. As it feeds amongst the bowlders 

 in the bed of the torrent it is lost to view in the midst of the stones. 



Some of the birds are not thus protected. But in such cases they 

 are able to defend themselves from enemies or have special places 

 into which they can escape. The raven, the steppe eagle, the kite, for 

 example, are so powerful that they need no protection. Certain little 

 birds, like the sparrows and accentors, are conspicuous, but they 

 keep near villages or piles of stone amongst which they can escape 

 from birds of prey. 



We see numerous examples amongst other creatures. The lizards 

 on the plateau are very variable in coloration. Some are uniformly 

 sandy, others coarsely speckled, but all harmonize with the arid soil. 

 There are different kinds of grasshoppers that haunt special situa- 

 tions. One, a large central Asian migratory species, is rich green in 

 color and li^•es in patches of fresh grass. Another, a new genus, 

 minute and wingless, lives on the moraines and decomposing granite 

 as high as 18,000 feet. It is finely mottled in grey and black, and 

 difficult to see because it closely resembles one of the granite flakes. 

 There is a third kind which keeps to tracts of coarse loose sand. In 

 its color scheme are patches of blue and red, and these harmonize 

 with similar colors in the grit. Still another kind haunts the water- 

 worn pebbles on the banks of the Chiblung Chu. This little grass- 

 hopper is a uniform blue color, and exactly the same shade as the 

 layer of stones. 



It would be tedious to mention all the other examples. But I must 

 refer to the high-altitude moths which frequent the moraines at 

 17,000 feet. These resemble a species of tiny Annrta. Their under 

 surface is very conspicuous, but is concealed when the insect alights 

 on the rock. Their upper surface, on the other hand, is a mottled 

 grey, which blends with the granite and the decomposing grit. 



Thus we see how important is protective coloration in the struggle 

 for existence at these great heights. It is in the vast and open tracts, 

 the deserts, the snows, the elevated wastes, that we have this prin- 

 ciple most lavishly displayed. The reason for protection of this 

 kind is clear. In the wilderness hiding places are seldom available. 

 There are no trees, no scrub, no profusion of grass in which the 

 animals can conceal themselves when enemies approach. To avoid 

 destruction they must seek evasion of some sort. Their only chance 

 is to resemble their natural surroundings and escape by being passed 

 unseen. 



I pass to another problem. How do the animals of these high 

 altitudes adapt themselves to the physical conditions that exist? 

 Consider first their reaction to the wind. Tibet is notorious for its 

 fierce winds. The morning sun heats the surface of the plateau, the 



