CASES OF ADAPTATIOX 145 



struggles with each other, fall out of the nest and quickly 

 perish. 



What wonderful perfection of the senses must there be in 

 these various parent birds; what acuteness of vision or of 

 hearing; what rapidity of motion, and what powerful instinct 

 of jDarental love, enabling them to keep up this high-pressure 

 search for food, and of watchfulness of their nests and j^oung, 

 on the continuance of which, and its unfailing success, the 

 very existence of those young and the continuance of the race 

 depends. But all this perfect adaptation in the parent birds 

 would be of no avail unless the insect tribes, on which alone 

 most of them are obliged to depend, were as varied, as abun- 

 dant, and as omnipresent as they actually are ; and also imless 

 vegetation were so luxuriant and abundant in its growth and 

 so varied in its character, that it can always supply ample food 

 for the insects without suffering any great or permanent injury 

 to the individual plants, much less to any of the species. 



By such considerations as these we learn that what we call 

 insect-pests, when they are a little more abundant than usual 

 in our gardens and orchards, do not exist for themselves alone 

 as an apparently superfluous and otherwise useless part of the 

 great world of life, but are, and must always have been through- 

 out long past geological ages, absolutely essential for the origina- 

 tion and subsequent development of the most wonderful, 

 delightful, and beautiful of all the living things around us — 

 our garden friends and household pets, and sweet singers of 

 the woods and fields. Without the myriad swarms of insects 

 everywhere devouring a portion of the new and luxuriant vege- 

 tation, the nightingale and the lark, the wren, the redbreast, 

 and the fairy-like tits and goldcrests might never have come 

 into existence, and if the supply failed would now disappear 

 for ever! 



The Uses of Mosquitoes 



If now we go beyond our OAvn country and see how birds 

 fare in distant lands, we find the key to many of the secrets 



