FOOD HABITS OF THE VIREOS 25 
ary, when according to our point of view few should be found, 
they amount to 14.1 per cent. The yearly average, from the data 
available, is 6.2 per cent. 
Spiders. — Except for February, spiders were eaten in all months of 
the year that are represented by stomachs. The percentage is never 
high, December with 6.83 being the maximum and June next with 
4.16 per cent. The average for the eight months is 2.05 per cent. 
VEGETABLE FOOD 
The record of vegetable food for the Hutton vireos is fragmentary, 
though coinciding so far as it goes with the known habits of other 
species of this family of birds. Except for months when no vegetable 
matter was found in the stomachs, the known data show a steady rise 
in the quantity eaten as the year approaches its end. The December 
percentage is 7.67 as compared with 0.7 in August. The yearly 
average is only 1.77 per cent. 
/ 
SUMMARY 
The evidence before us, though of questionable value because of 
the limited quantity of material, points to the fact that the Hutton 
vireos have a propensity for consuming undue numbers of ladybird 
beetles and rather fewer caterpillars than other vireos. Final judg- 
ment should be deferred, however, until additional material is avail- 
able for analysis. 
THE BELL VIREOS 
Vireo belli, subspp. 
The forms of the Bell vireos, like those of the Hutton, are birds 
primarily of the western United States, though their range extends 
much farther east than that of the Hutton vireos. In the willow 
thickets along water courses birds of this species may be found 
locally distributed in the greater part of the territory west of the Mis- 
sissippi River. Although the available material in the collection of 
the Biological Survey suitable for examination consists of only 52 
stomachs, these were collected in the months from May to August, 
inclusive, and serve as a fair index of the summer food. (See fig. 9.) 
Eleven additional, partially filled stomachs yielded other data con- 
cerning food items. Nothing can be said of the winter food at this 
time. 
ANIMAL FOOD 
Nearly all (99.3 per cent) of the food taken is of animal origin, such 
forms as bugs, beetles, caterpillars, and grasshoppers predominating. 
Eemiptera. — Bugs make up 34.43 per cent of the summer food of 
the Bell vireos. Of these about a quarter (9.34 per cent of the total 
food) are referable to the family of stink-bugs (Pentatomidae). 
More stink-bugs are eaten early and late in summer than in July and 
August. On the other hand, the rest of the hemipterans show a 
steady decrease as the season advances. In May more than half the 
hemipterous food was made up of bugs other than stink-bugs; June 
shows a decrease to 28.07 per cent, July to 11.61 per cent, and in 
August only 4 per cent belongs in this category. 
