320 Nature's Militia 



were allowed to live. That we do not have a yearly 

 plague of flies is due solely to the vigilance of the 

 birds. 



Look, again, at the country about Torgau on the 

 Elbe, where, a few years ago, birds were so scarce that 

 a large sum was spent yearly on the destruction of 

 grubs and caterpillars, to save the forest from utter 

 ruin ; yet all that human ingenuity could devise was 

 quite inadequate ; 800 acres of fir were entirely 

 stripped one year, and at the same time so much 

 grass was devoured that it was necessary to import 

 hay. In Hesse, too, all efforts to deal with a similar 

 plague of caterpillars were equally vain ; and it was 

 noticed that they were especially destructive where 

 there were few trees to divert their attention and 

 to attract the birds. 



The shrew-mouse, hedgehog, mole, lizard, frog, toad, 

 bat, and some of the beetles, are all excellent insect- 

 hunters, and the wasp and ichneumon- fly do good 

 work against caterpillars. But though their services 

 are valuable, the birds do more than all besides, each 

 kind in its own especial department. Some pick 

 insects, or their eggs, from the leaves, others from the 

 bark ; some dig them and their chrysalids from the 

 earth, others catch them as they fly. 



And what quantities they devour! for their digestion 

 is very rapid, and whereas human beings require only 

 a few ounces of dry food a day, they swallow a quan- 

 tity which is equal to their own weight. Think of it ! 

 the weight of a bird in insects ; green flies, for 

 instance. 



One redstart, kept in a room, has been known to 

 eat 600 flies in an hour; and one blackcap has cleared 



