10 The Regulative Action of Birds upon Insect Oscillations. 



to ninety-five. Again two-thirds of the food consisted of canker- 

 worms. The same little borer (^Psenocerus) eaten by so many of 

 the smaller birds in this orchard, made fifteen per cent, of the 

 food; and an Aphodius and an undetermined carabid bring up 

 the ratio of the Coleoptera to nineteen per cent. Four per cent, 

 of ants, a few gnats (five per cent.), and traces of Hemiptera and 

 mites were the only other elements detected. 



Dendroeca virbns, Gm. Black-throated Green Warbler. 



A single specimen of this migrant was shot in 1882. Seventy 

 per cent, of its food consisted of canker-worms, fifteen per cent, 

 of Psenocerus, and five of undetermined Hemiptera. The remain- 

 ing ten per cent, was made up of trivial numbers of Hymenop- 

 tera, gnats, coleopterous larvae and mites. 



Geothlypis trichas, L. Maryland Yellow-throat. 



This resident warbler occurred but sparingly in the orchard. 

 One specimen was seen in 1881, and two were obtained in 1882. 

 Lepidoptera made four-fifths of their food, about equally canker- 

 worms and undetermined caterpillars. A few Staphylinidse and 

 some specimens of Psenocerus composed the eight per cent, of 

 Coleoptera. A small hemipter (Piesma ciiierea) amounted to five 

 per cent., and four per cent, was gnats. 



B %i m m a T y of the Family. ^ 



Of the warbler family as a whole, as represented by these 

 fifteen specimens, I need only remark that fourteen of the birds 

 had eaten canker-worms, which composed nearly or quite two- 

 thirds of the food of the group; that ten per cent, consisted of 

 Psenocerus supernotatus^ and that the remaining averages, with 

 the exception of six per cent, of undetermined caterpillars, were 

 so much subdivided as to have little or no significance. 



VIREONID^. Vireos. 



ViEBO GiLVTJS, V. Warbling Vireo. 



Three specimens of this little bird were shot, of purely insect- 

 ivrous habit. They had eaten canker-worms to the amount of 

 forty-four per cent.; and other caterpillars made thirty-five per 



