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 larva? of the 

 brown-tail moth. These larvae 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 E. 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 ine twenty minutes ; took eight gipsy moth 

 larvae, several larvae 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 



