INSECTS AND THEIR REMEDIES. 117 



in part, at least, by the fact, that the number of cater- 

 pillars eaten is doubtless overestimated, in comparison 

 with hard insects, as their flexible skins remain in the 

 stomachs of birds longer than the hard structures of in- 

 sects. This is exactly contrary to the usual supposition, 

 but the frequent occurrence of numbers of the emptied 

 and twisted skins of cut-worms in the stomach, still rec- 

 ognizable as Noctuidce, when not even a fragment of a 

 single head remains, is sufficient evidence that the hard 

 parts break up and disappear before these delicate but 

 yielding skins. Secondly, while our knowledge of the 

 food of arctians, cut-worms, and grasshoppers, is suf- 

 ficiently definite and full to enable us to predict with cer- 

 tainty exactly what would happen, if those eaten by the 

 blue birds were allowed to live and multiply, we have not 

 the same complete and certain knowledge of the food and 

 habits of the different genera of ichneumonidas, the 

 ground-beetles, the soldier-bugs and soldier-beetles. One 

 hundred blue birds, at thirty insects each a day, would 

 eat in six months about half a million insects. If this 

 number of birds were destroyed, the result would be the 

 preservation of about one hundred and seventy thousand 

 caterpillars (ninety thousand of them cut-worms), twenty 

 thousand leaf-chafers, ten thousand curculios, and eighty- 

 five thousand crickets, locusts, and grasshoppers. 



"How this horde of marauders would busy itself, if 

 left undisturbed, no one can doubt. It would eat grass 

 and clover, and corn and cabbages, inflicting an immense 

 injury itself, and leaving a progeny which would multi- 

 ply that injury indefinitely. On the other hand, would 

 the two hundred thousand prcdaceous beetles and bugs, 

 spiders and ichneumons, either prevent or counterbal- 

 ance these injuries? I do not believe that we can say 

 positively whether they would or not. In a discussion 

 of the natural checks upon the cut- worm, Prof. Riley, in 

 his First Report as State Entomologist of Missouri, men- 



