154 USEFUL BIRDS. 
and the trunks of the trees appeared as if smoked. The 
enormous secretion 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 such quantities that it extended 
in a discolored circle from six to eight inches from the base 
of each tree. This information comes from the above-men- 
tioned circular. 
If the birds had been engaged for more than two weeks in 
clearing these insects from the few pear trees about my home, 
there must have been a great number of insects on those trees, 
for the pests are so small that each bird might eat thousands 
of them in a day. At the time of my return the insects were 
evidently becoming scarce ; but the birds persevered in their 
attentions to those trees, until in a few days I could not dis- 
cover a single specimen of the insect ; but even after that they 
looked the trees over occasionally, and still foundafew. By 
the end of another week, however, they had exhausted the 
supply, and, although they were seen occasionally in the 
woods, they seldom visited our trees. Apparently this was 
an incipient outbreak of a pest, brood after brood of which 
had probably been attacked by birds during the summer. 
As autumn came on, and the summer Warblers left on their 
southern migration, the last brood developed. The late- 
coming Warblers found them, and eagerly completed the task 
left unfinished by the summer birds. The pear trees had con- 
tinued to bear both foliage and.fruit as usual, and showed 
no injury. They will probably receive a similar protection 
next year. 
Dr. Howard intimates in his bulletin that the causes 
* which control the increase and decrease in numbers of this 
insect are not fully understood. Here is one agency of 
control that we can understand. It would be interesting 
to know to what extent this insect is distributed in Massa- 
chusetts, and how much the birds are doing to control it. 
These insects are so tiny as to escape observation, and this 
episode would have passed unrecorded, like so many others 
of its kind, had I remained away from home a few days 
longer. 
