174 A NATURALIST IN HIMALAYA 



organs of touch. These creatures possess, so far as 

 I could see, no trace of antennse, and are therefore 

 deprived of one organ very essential to insect life. 

 The conjecture of course arises that to a land insect 

 an antenna is a very necessary organ, but for a water 

 insect the hairs on the tips of the tarsi can fulfil the 

 function better since the detection of surface vibra- 

 tions is so important to its life. When the insects left 

 the land and sought an existence in the water the 

 antennse underwent degeneration and the sensitive 

 organ was developed elsewhere. Nor is it difficult to 

 picture the organs in an intermediate state, when the 

 antennae were degenerate and the sensitive hairs only 

 partially developed. 



It is not unreasonable to believe that water insects 

 attained their present mode of life in the pools and 

 streams as a consequence of a gradual change from 

 terrestrial to aquatic habits in remote ancestors that 

 once lived upon the land. In this connection it is 

 interesting to observe that these water-boatmen will 

 occasionally scramble out of the pool to take a short 

 walk along the bank, and when they do this, they 

 revert to the normal insect posture ; they no longer 

 move upon their backs, but walk about on their legs 

 after the manner of their terrestrial ancestors. 



In the society of the streams and pools all the 

 members live in continual conflict. I passed many 

 evenings watching the incessant struggle for life. 

 Not a cloud in the clear sky ; not the gentlest breeze ; 

 not a sound in the mountains to disturb the tranquil 

 scene. One would think that in these placid pools 

 Nature was happy and at peace. But no. War and 

 destruction reign everywhere in Nature. As I walk 



