134 INSECTS 



nomically harmless insects furnish a large percentage 

 of the food: ants, flies, fly larvae in excrement and 

 similar species. Another is, that a great many posi- 

 tively useful insects are taken ; less so those of absolute 

 importance to man by reason of their direct contri- 

 butions than those indirect friends, the predatory and 

 parasitic forms; and spiders may for this purpose be 

 counted as useful insects. Furthermore birds do not 

 discriminate between insects that are parasitized and 

 those that are not. Hence in eating cut-worms there 

 is at least an even chance that parasitized forms are 

 taken as freely as those not so infested. In eating a 

 parasitized specimen the only benefit derived by cut- 

 ting short its life is the saving of its food for a few days, 

 because it could not have come to the reproductive 

 stage anyway; while a positive harm has been done 

 in cutting short the parasites which might have de- 

 stroyed a hundred cut-worms the season following. 

 It is always possible to draw a variety of conclusions 

 from a list of insects found in bird stomachs, and that 

 generally drawn, to wit, that birds are always of very 

 great importance to the farmer and fruit-grower, is 

 usually no more warranted than the contrary one that 

 birds are of no use whatever. 



There never yet was an apple orchard kept free 

 from codling moth by birds no matter how much chance 

 the birds had: in fact in neglected old orchards where 

 birds and other animals are never disturbed it is rather 

 the exception to find a fruit free from insect attack. 

 The same is true of the plum curculio. There never 

 yet was a field of grain freed of green-fly by birds, nor a 

 tree of any kind saved by them from destruction by San 

 Jose scale. In many cases woodpeckers do more real in- 

 jury to a tree than the larva they get out would have 

 done, and the elm in a grove where birds hold undisturbed 



