VIII 



CASES OF ADAPTATION 131 



broader aspects of adaptation in the organic world, which, 

 so far as I am aware, have hitherto received little attention. 



Some Aspects of Organic Adaptation 



Though such a very obvious fact, it is not always kept 

 in mind, that the entire animal world, in all its myriad 

 manifestations, from the worm in the soil to the elephant 

 in the forest, from the blind fishes of the ocean depths 

 to the soaring sky-lark, depends absolutely on the equally 

 vast and varied vegetable world for its very existence. It 

 is also tolerably clear, though not quite so conclusively 

 proved, that it is on the overwhelming variety of plant 

 species, to which we have already called attention, that the 

 corresponding variety of animal species, especially in the 

 insect tribes, has been rendered possible. 



This will perhaps be better seen by a reference to one 

 of the best - known cases of general adaptation, which, 

 because so common and obvious, is often overlooked or 

 misunderstood. All lovers of a garden are apt to regard as 

 an unmitigated evil those swarms of insects which attack 

 their plants in spring, and in recurrent bad years become 

 a serious nuisance and commit widespread devastation. At 

 one time the buds or leaves of their fruit trees swarm with 

 various kinds of caterpillars, while at others even the oak 

 trees are so denuded of their leaves as to become an eyesore 

 in the landscape. Many of our common vegetables, and 

 even the grass on our lawns, are in some seasons destroyed 

 by swarms of wire -worms which feed on their roots. 

 Turnips, radishes, and allied plants are attacked by the 

 turnip-fly, a small jumping beetle whose larva lives in the 

 leaf itself, and which often swarms in millions. Then there 

 are the aphides and froghoppers on our roses and other 

 shrubs or flowers, and grubs which attack our apples, our 

 carrots, and most other crops ; and all these the gardener 

 usually regards under the general term " blight," as a serious 

 blot on the face of nature, and wonders why such harmful 

 creatures were permitted to exist. 



Most professional gardeners would be rather surprised to 

 hear that all these insect-pests are an essential part of the 

 world of life ; that their destruction would be disastrous ; 



