124 USEFUL BIRDS. 
serve the usefulness of birds as destroyers of plant lice and 
hairy caterpillars, and we determined to have both insects 
and birds watched at intervals through the spring and 
summer, that others might learn much that a lack of time 
rendered it impossible for us to determine by personal ob- 
servation. It was evident that certain birds were living very 
largely at this time on plant lice and three or four species 
of hairy caterpillars, and we wished to learn whether they 
and others would follow up this practice through the spring, 
and also whether they were learning to eat the larve of the 
brown-tail moth. These larve are provided not only with 
long hairs but with a coating of short, loosely attached hairs 
on the posterior part of the body, which are easily detached, 
barbed like the quills of a porcupine, and so tenacious that 
they will work quickly into the human skin and cause a vio- 
lent irritation and an itching eruption, which lasts for several 
days. It was to be expected that these, more than any other 
hairy caterpillar, would prove distasteful to birds, but the re- 
sult of the investigation that followed showed that birds were 
learning how to manage them. Messrs. Charles EK. Bailey 
and F. H. Mosher, both woodsmen and thoroughly compe- 
tent observers, well acquainted with both birds and insects, 
were instructed to make frequent visits to places where the 
conditions were such that they could readily observe the 
feeding of birds on hairy caterpillars and plant lice. They 
were asked to take notes and report the results each day. 
In order to give the reader a clear idea as to the character of 
the evidence thus secured, some of their field notes are tran- 
scribed below. The following notes are from Mr. Mosher’s 
reports : — 
May 26, 1898.—I went to the park near Hemlock Pool, Stoneham. 
An Oven-bird stayed near me twenty minutes; took eight gipsy moth 
larvee, several larvee that I could not determine, and many plant lice; 
then hopped to the ground and walked away, searching in the leaves. 
Three Chickadees came to the trees, and two of them took a gipsy 
larva each. They were picking plant lice and scales from the bark, and 
were picking off the loose bark, but I could not see what they got from 
beneath it. Two Black and White Warblers flitted from tree to tree, 
picking something from the bark and leaves, and were particularly busy 
