INSECTS IN RELATION TO OTHER ANIMALS 287 
served. Froma study of one hundred and eight Illinois speci- 
mens, Forbes finds that seventy-eight per cent. of the food for 
the year consists of insects, eight per cent. of Arachnida, one 
per cent. of Julidze and only thirteen per cent. of vegetable 
matter, edible fruits forming merely one per cent. of the entire 
food. The insects eaten are mostly caterpillars (chiefly cut- 
worms), Orthoptera (grasshoppers and crickets) and Cole- 
optera (Carabide and Scarabeide). Though some of the 
insects are more or less beneficial to man, such as Carabidze 
and Ichneumonidz (respectively predaceous and_ parasitic), 
the beneficial elements form only twenty-two per cent. of the 
food for the year, as against forty-nine per cent. of injurious 
elements, the remaining twenty-nine per cent. consisting of 
neutral elements. The food of the nestlings, according to 
Judd, is essentially like that of the adults, being “ beetles, 
caterpillars, grasshoppers, spiders and a few snails.” 
Other Insectivorous Birds.—Weed and Dearborn, from 
whose excellent work the following notes are taken, find that 
the common chickadee devours immense numbers of canker- 
worms, and that more than half its food during winter con- 
sists of insects, largely in the form of eggs, including those of 
the common tent caterpillar (C. americana), the fall web- 
worm (Hf. cunea) and particularly plant lice, whose eggs, 
small as they are, form more than one fifth of the entire food; 
more than four hundred and fifty of them are sometimes eaten 
by a single bird in one day, and the total number destroyed 
annually is inconceivably large. The house wren is almost 
exclusively insectivorous, feeding upon caterpillars and other 
larvee, ants, grasshoppers, gnats, beetles, bugs, spiders, and 
myriopods. The swallows, also, are highly insectivorous; 
“most of their food is captured on the wing, and consists of 
small moths, two-winged flies, especially crane-flies, beetles in 
great variety, flying bugs, and occasionally small dragon-flies. 
The young are fed with insects.” Ninety per cent. of the food 
of the kingbird “ consists of insects, including such noxious 
species as May-beetles, click-beetles, wheat and fruit weevils, 
