. Bulletin - Biological Survey. Zoology, Economic. FOOD BEKEFIOIAL m EFFECT ON AGRICULTURE. 23 FOOD BENEFICIAL IN EFFECT ON AGRICULTURE. The beneficial part of the food of sparrows is made up of insect pests and the seeds of weeds. Insect pests amount to from 10 to 20 per- cent of the year's food, and are for the most part grasshoppers (Acri- didse and Locustid^e), caterpillars, principally Noctuidse (that is, cut- worms, army worms, and their allies) and some Geometridae, such as cankerworms and their allies, and beetles of various families—Chry- somelidse or leaf-beetles, Elateridae or click
. Bulletin - Biological Survey. Zoology, Economic. FOOD BEKEFIOIAL m EFFECT ON AGRICULTURE. 23 FOOD BENEFICIAL IN EFFECT ON AGRICULTURE. The beneficial part of the food of sparrows is made up of insect pests and the seeds of weeds. Insect pests amount to from 10 to 20 per- cent of the year's food, and are for the most part grasshoppers (Acri- didse and Locustid^e), caterpillars, principally Noctuidse (that is, cut- worms, army worms, and their allies) and some Geometridae, such as cankerworms and their allies, and beetles of various families—Chry- somelidse or leaf-beetles, Elateridae or click-beetles, and Rhyncho- phora or weevils. Conspicuous among the genera of beetles met with in stomachs of birds are Systena, Epitrix, Odontota, Limonius, Dras- terius, Sitones, and Phytonomus. Bugs are eaten to an unimportant extent, and constitute about 1 percent of the food. The plant-feeding forms include such Heterpptera as some of the smaller soldier bugs (Pentatomidse), leaf-bugs (Capsidse), a few such Homoptera as leaf- hoppers (Jassidse), and in very rare instances plant-lice (Aphidid?e). Insects seldom form more than a third of the food of adult sparrows for the year, but their nestlings are practically entirely insectivorous; on which account these birds, in raising from two to three broods a season among agricultural crops, do their greatest good as destroyers of insect pests by cramming countless num- bers of caterpillars and grasshoppers down the throats of their ravenous young. Some grasshoppers are much —Rocky Mountain locust (after more injurious than others. The most ^^togyT"^ '''' ""'^'''^^ ""' "'''''" destructive species is the Rocky Moun- tain locust {Melanoplus spretus—see fig. 12), which at intervals invades the plains of the central United States in such numbers as to actually hide the sun. These insects travel onward, sweeping away every vestige of green vegetation in their path, and bringing destruction and
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