INSECTS INJURIOUS TO VEGETATION 35 



The most effective method of protecting a field from invasion 

 is to plow a deep furrow with steep sides around it and then pul- 

 verize the soil in the furrow so that the worms cannot climb out. 

 As a result they collect in the bottom, where they can be crushed 

 or killed by a dose of kerosene. 



Chinch Bug. — Another important enemy of field crops is the 

 chinch bug (Figs. 16 and 17), an insect about one fifth of an inch 

 long, with a black body and white wings folded over the back. 

 This insect has been principally injurious to small grains and corn 

 in the Central and North Central States, the total damage during 

 the years 1850 to 1909 being estimated at $350,000,000. The 

 bugs travel from field to field on foot, although they possess wings, 

 and like the army worm may be stopped in their march by a 

 steep furrow plowed in their path. A narrow strip of coal tar 

 is also an effective barrier to their progress. 



Other Insects Injuring Field Crops. — Other notorious pests 

 of field crops are the grasshoppers (see Chap. II); the cut- 

 worms (Fig. 18, A), which have a habit of gnawing off the stems of 

 plants just at the surface of the ground; the Hessian fly (Fig. 

 i8,B), which attacks the stalks of wheat and causes an average 

 loss of about 10 per cent each year; the green bug (Fig. 18, C), 

 a plant louse which sucks the juices of oats, wheat, barley, and 

 corn, stunting or killing the plants ; the corn-ear worm (Fig. 

 18, D), which eats into the ears of corn, destroying from 2 to 

 3 per cent of the crop annually with an estimated cash value 

 of from thirty to fifty million dollars; the alfalfa weevil (Fig. 

 18, E) in the West; and the cotton boll weevil (Fig. 18, F) of 

 the South, which damages cotton every year to the extent of 

 about twenty million dollars. 



Insects Injuring Garden Vegetables. — Potato Beetle. — 

 We are perhaps more familiar with insects that injure garden 

 vegetables, such as the potato beetle and cabbage butterfly, than 

 with those that destroy field crops. The potato beetle (Fig. 19) 

 was, up to the year 1885, a harmless insect, living in the Colorado 

 region. It fed upon certain common weeds, but when the Irish 



