182 NORTH AMERICAN INSECTS. 



man and beast would soon be destroyed by starvation, 

 but it is undoubtedly one of the designs of nature 

 that these should increase immensely for the very 

 purpose of furnishing sufficient nourishment for the 

 birds and other winged animals which make them 

 their principal food. It is ascertained that a single 

 robin or woodpecker, and many others of the war- 

 blers, carry every day about fifty grubs or caterpillars 

 to their nests as food for themselves and their young. 



Now if there were only one million of these birds 

 of which each one devours 6000 caterpillars during 

 the months of April, May, June, and July, by no 

 means a large computation, the number of caterpill- 

 ars and grubs thus destroyed will amount to 6,000,- 

 000,000 annually. 



Caterpillars are therefore of great use to us in fur- 

 nishing so abundant food and nourishment for the 

 birds, which enliven and embellish the country with 

 their happy songs and their beautiful plumage, and 

 which themselves supply us with a palatable and de- 

 licious article of food. 



Caterpillars are also destroyed by various kinds of 

 vein-winged insects, which are not so useful to man, 

 principally by different species of the Ichneumon fly, 

 which with her ovipositor thrusts one or several eggs 

 into the body of the caterpillar, upon the flesh of 

 which the maggots of these flies subsist, until they 

 come out as perfect flies, of course destroying the 



