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. 
Dendrceca virens, 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 cinerea) amounted to five 
per cent., and four per cent, was gnats. 
Summary of the Family. 
Of the warbler family as a whole, as represented by these 
fifteen specimens, 1 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. 
YIREONIDiE. Yireos. 
Vireo gilvus, V. Warbling Yireo. 
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 oaterpillars made thirty-five per 
