4 
OHIO EXPERIMENT STATION: BULLETIN 250 
of grain during migrations. Certain species, highly beneficial in nor¬ 
mal numbers, become destructive when their numbers are greatly 
increased. The whole economic problem hinges on the balance that 
can be preserved in nature. An increased food supply would tend to 
increase the number of birds feeding thereon; when the supply is 
materially decreased, the birds must look elsewhere for food, and 
this may result in their becoming destructive. 
From the beginning of time, the organic forces of nature have 
been engaged in constant conflict, each against the other, but maintain¬ 
ing, on the average, a stable balance until the advent of civilized man. 
In our own country this equilibrium was preserved until the Pilgrim 
Fathers began to hew homes out of the virgin forest. Fields of maize 
and wheat supplanted the forest, affording an abundant supply of 
juicy, tender food to many insects that formerly were dependent 
upon the forest. The destruction of the forest has caused a steady 
decrease in the numbers of birds, dependent thereon for protection, 
food, and nesting sites; this, with the destruction of many birds for 
food or other purposes, has greatly reduced this natural check on 
insect life. Many species have adapted their manner of living to the 
changed conditions, some of which find present conditions even more 
favorable than those prevailing formerly. Other species, native to 
the western plains have, since the settling of the country, extended 
their ranges eastward. 
4 
AS DESTROYERS OF INSECTS 
The loss to cultivated crops, through insect ravages, is stupen¬ 
dous. Such loss to cereal crops, animal products, and farm wood- 
lots has been estimated at ten percent of the value, and twenty per¬ 
cent has been computed for truck crops and fruits. (Marlatt). 
Of the Field. A few of the important insects detrimental to 
Ohio field crops are the Colorado potato beetle, the white grub of 
the May beetle, chinch bug, army worm, wire worm, grasshoppers, 
crickets, and various cutworms. In normal numbers, their injury is 
not so apparent, but when conditions are favorable for their increase, 
any one of these may become a serious pest. Spraying is practicable 
for but few field crops, so help must be looked for from other sources. 
At such times, birds must be rated as among man’s most important 
allies. 
Cutworms are among the most destructive of larvae, sometimes 
almost totally destroying a crop, Many species of birds aid in their 
destruction, and for a few species these insects, when obtainable, 
constitute a large part of their food. The white grub of the May 
beetle, on account of its subterranean habits, is difficult to combat. 
