OUR DEBT TO THE SWALLOWS 153 



lions of dollars a year is calculated to be 

 the money value of our birds to agriculture. 

 In the state of Illinois it has been estimated 

 that if the operations of birds were stopped 

 for a period of seven years, the entire state 

 would be covered with insects to the number 

 of one to a square inch. 



Because of their habits of living in the air 

 and feeding upon the insects they catch on 

 the wing, the several species of the swallow 

 family known to us form one of the most 

 serviceable divisions of this vast, protecting 

 army. Our Department of Agriculture, in a 

 recent paper, says: — 



" From the standpoint of the farmer and 

 the orchardist, perhaps no birds more useful 

 than the swallows exist. They have been 

 described as the light cavalry of the avian 

 army. Specially adapted for flight and un- 

 excelled in aerial evolutions, they have few 

 rivals in the art of capturing insects in mid 

 air. They eat nothing of value to man ex- 

 cept a few wasps and bugs, and in return for 



