30 



small certain marked branches are chosen for observation, or certain 

 nests, webs or tents are marked and watched at close l-ange. One ob- 

 server has even counted the number of caterpillars on a branch, watched 

 the birds feed upon them and then counted the number left alive 



The results of the earlier observations were published in the report 

 on the gypsy moth, issued by the State Board of Agriculture in 1896.* 



It was then proved conclusively that thirty-eight species of birds were 

 destroying the gypsy moth in one or more of its forms, and thirty-one 

 of these were feeding on the caterpillars. Since that time several birds 

 have been added to the list, and much more has been learned as to the 

 comparative usefulness in this respect of several species. 



The discovery of another introduced pest, the brown-tail moth, Eu- 

 prochs chrysorrhoea, in Massachusetts in 1897, has stimulated further 

 observation, and incidentally the feeding of birds on other hairy cater- 

 pillars has been noticed. 



It is not the intention of the writer now to republish the result of the 

 observations given in the report on the gypsy moth in 1896, but to place 

 before the reader some facts observed that year and since. From the 

 mass of observations on the food of birds a part has been selected of 

 those which refer to the two introduced European species — the gypsy 

 moth, Porthetria dispar, the brown-tail moth, Euproctis chrysorrhcea — 

 and two common American pests — the tent caterpillar, Clisiocampa amer- 

 icana, and the forest tent caterpillar, C. sylvalica. In these four species 

 we have typical examples of genera, the larvae of which have been con- 

 sidered especially distasteful to birds on account of the hairs with which 

 they are covered. The caterpillars of the brown-tail moth would appear 

 to be a particularly disagreeable morsel to swallow. They are not only 

 furnished with long, bristly hairs, but the hinder segments of the body 

 are also supplied with minute, shorter hairs which are barbed, somewhat 

 like the quills of the porcupine. These hairs produce veiw disagreeable 

 consequences when brought in contact with the human skin, into which 

 they work their way and there become the source of a serious and long- 

 continued irritation.f Many people in the district infested by the brown- 

 tail moth have been seriously inconvenienced by this cause and the ser- 

 vices of physicians in the region infested have been widely sought for a 

 remedy. The irritation resembles that caused by poison ivy and no in- 

 fallible cure has yet been found. One would think that a bird which 

 had inadvertently swallowed one of these creatures would not care to 

 repeat the experiment, but the observations of Mr. F. H. Mosher, a very 

 careful observer, show that as many species of birds feed on the brown- 

 tail caterpillar as upon the gypsy caterpillar, and some species eat quan- 

 tities of the former. 



Some of the hairs of the gypsy caterpillar possess an irritating prop- 

 erty, so that the sensation produced by them, when pressed against any 

 tender portion of the human skin, is similar to that produced by nettles. 



The hairs on the tent caterpillar do not seem to possess either of 

 these properties. But even these larvae do not appear a tempting morsel, 

 thickly covered as they are with long hairs. 



The forest tent caterpillar also is supplied with hairs sufficient to 

 secure it immunity from the attacks of birds if, indeed, such hairs con- 

 stitute any protection whatever. 



The Number of Hairy Caterpillars destroyed by Birds. 



In order to get a definite idea of the comparative usefulness of the 

 different species of birds in destroying hairy caterpillars, I have asked 

 Mr. Mosher to count the number of caterpillars each bird was actually 

 seen to eat during the time occupied in some of its visits to trees infested 

 by caterpillars. As examples of the capacity of birds' stomachs for this 



* " The Gvpsy Moth," Forbush-FernaUl, 1896. 



t Proc. 10th Ann. Meeting Assn. of Ec. Eats., Bui. 17, p. 27, Prof. C. H. Fernald. 



