68 FOOD HABITS OF THE GROSBEAKS. 
ANIMAL Foop. 
Insects and other animal matter eaten by the black-headed gros- 
beak amount to almost twice the bulk of the vegetable food, or 65.85 
percent of the total subsistence. These, then, should be regarded as 
the really staple foods of the species. While no single vegetable ele- 
ment was fed upon by more than 41 grosbeaks, certain items of the 
insect diet were chosen by more than a hundred, or over half of the 
birds examined. This fact suggests that if the majority of the insects 
preyed upon are noxious, the benefits conferred by the bird greatly 
outweighs the injury inflicted. 
Coming, then, to the economic status of the insects devoured, it 
appears from the results of the examination of 226 stomachs that 3.37 
percent of the bird’s food consists of ground beetles, fireflies, and 
ladybirds, which usually are considered beneficial; 2.56 percent is 
composed of wasps, ants, bees, ete., some of which are very useful, 
some innocuous or harmful; and 1.17 percent is made up of a great 
number of unrelated items, largely of neutral import, which, owing 
to the fact that they are rarely eaten, have little significance. Thus 
58.75 percent, or nearly three-fifths of the entire food, is composed al- 
most wholly of insects which are a constant menace to agriculture. 
Of the above classes the beneficial kinds deserve first consideration. 
The most important among them numerically are fireflies (Lam- 
pyride), which are almost uniformly carnivorous, both as larve and 
as adults. Since they do much to check the increase of many other 
insects, the destruction of large numbers would be injurious. Fifty- 
two of the grgsbeaks examined had fed upon fireflies to the extent of 
2.38 percent of the whole food. Both adults and larve were captured, 
from 5 to 19 of the former and from 12 to 30 of the latter being found 
im some stomachs. 
Among other useful insects which are attacked by the blackhead 
are the ground beetles (Carabide). Nineteen grosbeaks ate them, 
and they amount to 0.99 percent of the food. Since so few of these 
beetles are captured and as certain of them at times feed upon plants, 
the injury is too slight to be noticed. 
Three black-headed grosbeaks ate small ladybird beetles which prey 
upon scale insects and plant lice, two of them securing specimens of 
an Australian coccinellid (RAizobius ventralis, fig. 33), which was 
introduced into California for the express purpose of destroying scale 
insects. If the grosbeak destroyed many of these beetles, the bird 
would have to be given a black mark, but when it is considered that 
the blackhead feeds upon scale insects a large part of the time (more 
than a fifth of its food consisting of scales), it is surprising that so 
few of the ladybirds are devoured. 
Considerable king, however, was shown for another group, the 
Hymenoptera, part of which at least are beneficial. The most useful 
