INSECTS IN RELATION TO OTHER ANIMALS 243 



The Insect Food of Birds. " There are few groups of injurious 

 insects that enter so largely into the composition of the food of birds as 

 do the locusts, or short-horned grasshoppers, of the family Acridiidae 

 [now Locustidae]. The enormous destructive power of these insects 

 is well known, but our indebtedness to birds in checking their oscilla- 

 tions is less generally recognized." Professor Aughey, who has made 

 extensive studies upon the relation of birds to the Rocky Mountain 

 locust, found that upon one occasion 6 robins had eaten 265 of these 

 insects, 5 catbirds 152, 3 blue-birds 67, 7 barn swallows 139, 7 night 

 hawks 348, 1 6 yellow-billed cuckoos 416, 8 flickers 252, 8 screech owls 

 219, and i humming bird 4; while crows and blue- jays had eaten large 

 numbers of the locusts; and grouse, quail and prairie hen, enormous num- 

 bers. Even shore birds, such as geese, ducks, gulls and pelicans came to 

 share in the feast. Aughey estimated that the locusts eaten in one day 

 by the passerine birds' of the eastern half of Nebraska were sufficient to 

 destroy in a single day 174,397 tons of crops, valued at $1,743.97. 



Weed and Dearborn state that, of Hemiptera, Jassidae are very often 

 found in the stomachs of birds, and that aphids and their eggs form a 

 large part of the food of many of the smaller birds, such as the warblers, 

 nuthatches, kinglets and chickadees. A large proportion of the cater- 

 pillars of the Lepidoptera are eagerly devoured by birds, forming an 

 important element of the food of many species. The hairy caterpillars 

 are eaten by cuckoos and blue- jays and the large saturniid caterpillars, 

 such as cecropia and polyphemus, by some of the hawks. Almost all 

 kinds of Coleoptera are food for birds, but especially the grubs of Scara- 

 baeidae, which are eagerly devoured by robins, blackbirds, crows and 

 other birds. Of the Diptera, Itonididae and other gnats are eaten 

 by swallows, swifts and night hawks; while crane flies, Tipulidae, are 

 often found in the stomachs of birds. Among Hymenoptera, ants are 

 eaten extensively by woodpeckers, catbirds and many other species, as 

 are also Ichneumonidae and other parasitic forms these last by the 

 flycatchers in particular. 



The Regulative Action of Birds upon Insect Oscillations. The worst 

 injuries by insects are done by species that fluctuate excessively in 

 number as the result of variations in those manifold forces that act as 

 checks upon the multiplication of the species. 



In order to determine whether birds do anything to reduce existing 

 oscillations of injurious insects, Professor Forbes made studies upon the 

 food of birds which were shot in an Illinois apple orchard which was 

 being ravaged by canker-worms. In this orchard, birds were present in 



