360 BOAED OF AGRICULTURE. [Pub. Doc. 



One of them was noticed to take eleven canker-worms in 

 its beak at one time, and fly with them to the nest. The 

 vireos warblers, chickadees, cuckoos, orioles and chip- 

 ping sparrows were particularly active in catching canker- 

 worms, and the English sparrow killed them in considerable 

 numbers. 



If the thirty-six pairs of birds whose nests were found had 

 succeeded in raising their young, it is probable that they 

 would have disposed of most of the canker-worms in the 

 neighborhood. Five thousand of these larva? are sufficient 

 to strip a large apple-tree. One hundred and eight young 

 would have been reared, had each pair of birds raised three. 

 According to Professor Aughey's experience, sixty insects 

 per day as food for each bird, both young and old, would be 

 a very low estimate.* Suppose each of these one hundred 

 and eight birds had received its sixty insects per day, there 

 would have been 6,480 caterpillars destroyed daily. The 

 destruction of this number of caterpillars would be enough 

 to save the foliage and fruitage of one apple-tree. In thirty 

 days the foliage of thirty apple-trees could have been saved, 

 or 194,400 canker-worms destroyed. This does not include 

 what the old birds themselves would have eaten. 



In these observations the influence of insect parasites and 

 predaceous insects has not been entirely ignored. Hymen- 

 opterous parasites were not seen to be numerous, and as it 

 was a year when canker-worms were on the increase, it is 

 not probable that these parasites would have been a prime 

 force in reducing the numbers of the canker-worms had the 

 birds not been present. Even had they been numerous 

 they would have had little effect in checking the ravages of 

 the canker-worm during the present year, as their interest 

 is identical with that of the canker-worm, and they remain 

 in its body until it has finished feeding, allowing it to de- 

 foliate the trees before completing their deadly work upon it. 



We do not know to what extent such parasites are de- 

 voured by birds. This we could not ascertain without 

 shooting the birds, which would have defeated our main 

 object. No parasites of the tent caterpillar or canker-worm 



* First report United States Entomological Commission, 1877, page 342. 



