WHY DO ANIMALS BECOME EXTINCT? 185 



notably the rabbits, increased so enormously that in turn 

 a bounty was put on rabbits, the damage these animals 

 caused the fruit-growers being greater than the losses 

 among sheep-owners from the depredations of coyotes. 

 And so, says Dr. Palmer, "In this remarkable case of 

 legislation a large bounty was offered by a county in the 

 interest of fruit-growers to counteract the effects of a 

 State bounty expended mainly for the benefit of sheep- 

 owners !"i 



Professor Shaler, in noting the sudden disappearance 

 of such trees as the gums, magnolias, and tuUp poplars 

 from the Miocene flora of Europe has suggested that this 

 may have been due to the attacks, for a series of years, 

 of some insect enemy like the gipsy moth, and the 

 theory is worth considering, although it must be looked 

 upon as a possibility rather than a probability. Still, 

 anyone familiar with the ravages of the gipsy moth in 

 Massachusetts, where the insect was introduced by 

 accident, can readily imagine what might have been the 

 effect of some sudden increase in the numbers of such a 

 pest on the forests of the past. Trees might resist the 

 attacks of enemies and the destruction of their leaves for 

 two or three years, but would be destroyed by a few 

 additional seasons of defoliation. 



Ordinarily the abnormal increase of any insect is 

 promptly followed by an increase in the number of its 

 enemies; the pest is killed off, the destroyers die of 

 starvation and nature's balance is struck. But if by 

 some accident, such as two or three consecutive seasons 

 of wet, drought, or cold, the natural increase of the 

 enemies was checked, the balance of nature would be 

 temporarily destroyed and serious harm done. That 



'This state of things is still (1921) going on as may be seen by the 

 reports of the Biological Survey, Department of Agriculture. 



