118 TRUCK-FABMIKO AT THE SOUTH. 



tions two species of ichneumon 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 Eeport of the United States Entomological Commis- 

 sion, for 1877, we learn that the grasshopper is preyed 

 upon, at one or the other stage, by Agonoderus, Harpa- 

 lus, Amara, and other carabids; by soldier-beetles, sol- 

 dier-bugs, and spiders, and that certain ichneumonidae 

 parasitize the eggs. It seems probable, therefore, that 

 the beneficial insects eaten by blue birds include the spe- 

 cial enemies of the cut-worms and grasshoppers it de- 

 stroys, but he who knows best the small number of re- 

 liable observations upon which our general statements of 

 the food of predaceous insects rest, will have the most 

 hesitation in trusting them without reserve. The proba- 

 bilities seem to be against the blue bird, but the certain- 

 ties are, as yet, in its favor. Finally, I would call atten- 

 tion to the fact that we do not know that the normal 

 rate of increase among these carnivorous and parasitic 

 insects is not sufficient to keep their numbers full to the 

 limit of their food supply, and to furnish also a surplus 

 for destruction by birds. Just as a tree puts forth more 

 leaves than it needs, and sets more fruit than it can pos- 

 sibly mature; as an offset to the constant normal depre- 

 dations of insects, so there is much reason to suppose 

 that our insect friends have become adjusted to this 

 steady drain on their numbers. There are many consid- 

 erations involved here into which I can not at present 

 enter. It will suffice to say that all the evidence we have 

 of the increase and decrease of carnivorous insects, at- 

 tendant upon the increase and decrease of the insects 

 upon which they feed, tends to show that the real limit 

 to their multiplication is not destruction by birds, but a 

 deficient food supply, and that in relieving them from 

 their feathered enemies, we should only be giving a por- 



