490 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



beetles and sucking bugs attack the leaves and stems. The 

 minute whitish larvae of small flies lie in the stems or leaf axils 

 and drain the sap. Weevils ravage the stored grain. Cotton 

 has its peculiar pests, one of which alone, the notorious cotton 

 boll-weevil, that came into this country from Mexico only 

 twenty years ago, has in the last decade caused an annual 

 loss of not less than twenty-five million dollars. 



Grasses and forage plants have an exceptionally wide range 

 of insect enemies, and enemies that for the most part are very 

 difficult to fight successfully in any inexpensive way. Most 

 of their combating must be done by such general agricultural 

 methods as crop rotation, or very deep or unusually late or 

 early plowing, etc. 



The few grain, cotton, and forage crop pests described in the 

 following paragraphs comprise the ones of chief importance, 

 but there are many others to be taken into account. Students 

 should refer to sources of more inclusive and detailed informa- 

 tion concerning these pests. The bulletins of the government 

 and state bureaus of entomology are good sources for this 

 information. Sanderson's " Insect Pests of Farm, Orchard and 

 Garden," already mentioned, is a good recent manual. 



CORN 



The Western Corn-root Worm (Diabrotica longicornis) . 

 This is a slender larva, or grub, that bores into the roots of young 

 corn and seriously interferes with its development. Sometimes 

 these larvae will destroy the greater part of the root system so 

 that the plant either dies, or is easily blown over by the wind, 

 or, if it lives, is unproductive. The adult is a small bluish- 

 green, leaf-eating beetle about one-third of an inch long. The 

 eggs are laid in the ground in the fall near the roots of the corn 

 and do not hatch until the following spring. As the larvae feed 

 only on corn it is evident that a system of crop rotation will con- 

 trol the pest. 



The Southern Corn-root Worm (Diabrotica i2-punctata}. 

 The larva of this species is similar in appearance and habits to 

 the one just described, but it has a wider range of food plants. 



