No. 4.] BIRDS AND CATERPILLARS. 335 



are torn open by birds and all or nearly all of the caterpillars 

 in the webs destroyed. 



The most striking instance observed of the cheek exerted 

 by birds on the increase of hairy caterpillars was in George- 

 town, Mass., in July, 1899. Here a colony of the gypsy 

 moth had grown and flourished in the woods unknown to 

 any one until it was discovered in midsummer. The moths 

 had been increasing there without any check excepting their 

 natural enemies, and they had defoliated the trees and shrub- 

 bery on at least two acres of land, stripping both pine and 

 hard-wood trees. A vast swarm of caterpillars had been 

 at work there. It was noticeable, however, that the cater- 

 pillars were not nearly so numerous at the time of their dis- 

 covery as they had been in other localities where they had 

 not done so much injury ; in other words, there were not 

 enough caterpillars to account for the destruction of the foli- 

 age. The colony was near the edge of the woods, with a 

 field and meadow on one side and an orchard near by. Birds 

 abounded in the vicinity. So soon as one came within hear- 

 ing distance of the place cries of crows and blue jays were 

 heard in and about the edges of the stripped tract. Many 

 chickadees, tanagers, thrushes, warblers, sparrows, flycatch- 

 ers and cuckoos were about. At the foot of some of the 

 large trees hundreds of dead and dying caterpillars were 

 found which evidently had been injured by the beaks of 

 birds. Mr. Mosher watched the locality for a few days and 

 found many species of birds feeding on the caterpillars. He 

 noticed that whenever he left the locality many crows came 

 in and fed. There were very few parasites and other enemies 

 of the gypsy moth in the vicinity, and the conclusion natur- 

 ally arrived at was that enormous numbers of caterpillars had 

 been destroyed by birds. Thus only could the evident great 

 reduction in the numbers of the caterpillars be accounted for. 

 Many birds were destroying the moth in all its forms, and, 

 while they had not succeeded in suppressing the outbreak, it 

 was plain that they were exerting a strong restrictive influ- 

 ence upon the increase and spread of this injurious insect. 



