22 THE WONDER OF LIFE 



long since sped, and the caves are the home of legions of 

 bats. As the sun is setting a couple of falcons come over 

 the hill and fly restlessly to and fro over the river, keeping 

 a watchful eye on the mouths of the caves. Then kites 

 and jungle crows gather together till there are about a 

 hundred. The dramatic moment is at hand. Out comes 

 a single bat, then a pair, in puzzling jerky flight, eluding 

 the birds of prey, who are too experienced to be led off on a 

 profitless pursuit. There is a pause for a minute or two, 

 then a sudden rush of wings is heard, and the nightly sortie 

 begins. Like smoke from a dirty chimney on a stormy 

 day, the bats issue in a dense column, ten feet wide by ten 

 feet deep, in hundreds and thousands, so closely packed 

 that many are jostled into the river below. The falcons, 

 kites, and jungle crows have now their innings ; they fall 

 upon the sortie and, striking right and left, soon obtain all 

 they want. But the enormous majority of the bats escape 

 safely into the after-glow. It seems likely that the cease- 

 less sifting process is automatically regulated, else the 

 relatively weak and slowly reproducing race of bats would 

 long since have come to an end. Bats have such an unpre- 

 dictable kind of flight that they are very difficult to catch ; 

 when the birds reduce their numbers so that the crowd is 

 no longer closely packed, the nightly percentage of victims 

 will fall. It will no longer pay the birds to hunt them, 

 and there will be a close time till the numbers rise again. 

 A New Jersey naturalist describes a great host of mos- 

 quitoes, which were pursued and thinned by a large army 

 of dragon-flies, which were being in turn destroyed by a 

 big flock of birds. Similarly in mankind, while one tribe 

 is destroying another a more civilized power often bears 

 down upon the conquerors. We have referred elsewhere to 



