116 TRUCK-FABMIKG AT THE SOUTH. 



made by Prof. S. A. Forbes, of Illinois, of the stomachs of 

 eighty-six blue birds (Sialia sialis), and his observations 

 and conclusions.* Ten of the birds were shot in Feb- 

 ruary, twenty-one in March, thirteen in April, nine in 

 May, ten in June, nine in July, two in September, and 

 twelve in December, in Southern Illinois. The stomach 

 of a bird shot February 24th, contained thirty per cent, of 

 cut- worms; forty per cent, of crickets; five per cent, of 

 ichneumonidse; twenty-five per cent, of the larvae of the 

 two-lined soldier-beetle. After enumerating the contents 

 of the stomachs of all the birds, Prof. Forbes summarizes: 

 " What now shall we say of the economic relations of 

 this bird? According to the estimate of Mr. Walsh that 

 (reasoning from the comparative numbers of injurious 

 and beneficial insects, a bird must be shown to eat at 

 least thirty times as many injurious individuals as bene- 

 ficial ones, before it can be considered useful), the blue 

 bird does at least twenty times as much harm as good, 

 that is to say, the beneficial insects destroyed would 

 themselves have made away with twenty times as many 

 injurious insects as the birds themselves have eaten. 

 Admitting that Mr. Walsh's estimate was exaggerated, it 

 surely was not twenty times too large, and even if it 

 were, we could merely look upon the blue bird as harm- 

 less, indeed, but as useless also. And yet, in the face of 

 this, I venture to doubt that a case has yet been made out. 

 " In the first place, nothing has been learned of the food 

 of the young, and there is some reason for supposing 

 that birds select for their young, the softer kinds of in- 

 sects. This supposition, founded chiefly upon the state- 

 ments of M. Florent-Prevost, of Paris, is contradicted, 

 it is true, by observations of the food of the young mock- 

 ing-bird, and whatever deficiency of credit may be due 

 to this neglect of the food of the young, is compensated 



* From the " American Entomologist," 1880. 



