25 



and weeks following. Each morning under these trees a con- 

 siderable group of blackbirds could be seen which evidently had 

 been feeding on the newly issued cicadas. Scarcely a single 

 cicada escaped the sharp eyes of these birds. He says that the 

 absolute failure of these insects to establish themselves when 

 planted in such enormous numbers, even when the underground 

 period had been successfully passed, owing to the relentless on- 

 slaught of birds, is a striking illustration of what is happening 

 year after year with successive broods, especially in thinly 

 forested regions, and accounts for their great reduction in 

 number and the practical disappearance of local swarms for- 

 merly abundant. 1 



Birds sometimes clear plants and trees of insect pests before 

 the presence of these pests has been brought to our notice. In 

 November, 1905, on returning to Wareham after a long absence, 

 I noted a flock of myrtle warblers and some goldfinches that 

 were very busy among the apple trees, and w^ere searching with 

 particular diligence a pear tree near the house. I was told that 

 they had been at that occupation for about two weeks. I 

 realized at once that they must have been engaged upon those 

 leafless trees in the suppression of some insect pest. A careful 

 examination revealed the fact that the birds were working the 

 trees thus carefully for little cicada-shaped insects, which were 

 identified by Dr. L. O. Howard as the pear tree psylla (Psylla 

 pyri), a European pest introduced into this country. These 

 insects are extremely destructive to pear trees. Devastating 

 invasions have occurred in Maryland, Virginia and New Jersey. 

 These jumping plant lice are extremely prolific, having several 

 broods each year. In the infested Maryland orchards the 

 leaves and fruit fell, the latter before it was half grown. Enor- 

 mous secretions of honeydew that the hosts of these insects 

 produced from the sap of the trees fell like rain, drenching the 

 horses used in cultivating the orchard, and running down the 

 trunks in streams. On my farm, however, the birds which had 

 been engaged for two weeks in clearing these insects from the 

 pear trees had been so successful that it was difficult for me to 

 find any of the insects on the trees, and in a few days I could 

 not discover even a single specimen. But even after that the 



1 Proceedings, Entomological Society of Washington [District of Columbia], Vol. IX, 1907, 

 p. 18. 



