158 
The Food of Birds. 
before these delicate but yielding skins. Secondly, while 
our knowledge of the food of Arctians, cutworms and 
grasshoppers is sufficiently definite and full to enable us 
to predict with certainty exactly what would happen if 
those eaten by bluebirds were allowed to live and multi- 
ply, we have not the same complete and certain knowl- 
edge of the food habits of the different genera of Ichneu- 
monidae, the ground-beetles, the soldier-bugs and soldier- 
beetles. 
One hundred bluebirds, at thirty insects each day, 
would eat in eight months about 670,000 insects. If this 
number of birds were destroyed, the result would be the 
preservation, on the area supervised by them, of about 
70.000 moths and caterpillars (80,000 of them cutworms), 
12.000 leaf-chafers, 10,000 curculios and 65,000 crickets, 
locusts and grasshoppers. How this frightful horde of 
marauders would busy itself if left undisturbed, no one 
can doubt. It would eat grass and clover and corn and 
cabbage, inflicting an immense injury itself, and leaving 
a progeny which would multiply that injury indefinitely. 
On the other hand, would the 160,000 predaceous beetles 
and bugs, spiders and ichneumons either prevent or com- 
pensate 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- 
worms Professor Riley, in his First Report as State 
Entomologist of Missouri, mentions two species of Ich- 
neumon that parasitize the larva, credits the spined 
soldier-bug and the Carabid larva, Calosoma calidum, 
with its destruction, and says that some kinds of spiders 
are known to prey upon it. 
From the Report of the United States Entomological 
Commission for 1877, we learn that the grasshopper is 
preyed upon at one or the other stage by Agonoderus, 
Ilarpalus, Amara and other Carabids; by soldier-beetles, 
soldier-bugs and spiders ; and that certain Ichneumonidae 
parasitize the egg. It seems probable, therefore, that the 
beneficial insects eaten by bluebirds include the special 
enemies of the cutworms and grasshoppers it destroys; 
but he who knows best the small number of reliable obser- 
