FORAGING HABITS OF BIRDS. 159 



wills by night. It matters not in what stage of its ex- 

 istence the insect is destroyed; it is still demonstrable 

 that these minute creatures cannot be kept in check 

 unless they are attacked in all stages. Birds are their 

 only effectual destroyers. Man cannot check their mul- 

 tiplication or their ravages by artificial means. He 

 cannot even protect his garden. Their destructive and 

 infinite multiplication can be prevented only by Nature's 

 own agents, which she has created with this power. A 

 million of ichneumons would not do the work of a 

 dozen birds. 



