Some Special Injurious Insects 



173 



grain, and, after feeding on the starchy matter for about 

 three weeks, form a thin silken cocoon, from which it 

 emerges a few days later. About thirty-five days are 

 used in passing from egg to adult. Four to, possibly, eight 

 broods are formed during the year. When grain is stored 

 in bulk, only the surface layers are infested. Both the 

 weevils and moths are subject to attacks by parasites. 

 242. Preventing Injury to Stored Grain. To reduce 

 the injury to stored grain, use is made of repellants like 

 napthelene (so-called "moth balls"), salt, air-slaked 

 lime, and other substances which, while not poisonous, 

 drive the insect out. A temperature of 125 Fahr. is 

 sufficient to kill weevils, though more than 150 Fahr. 

 may be endured by dry grain without loss of ger- 

 minating power. Treating the grains to the vapors of 

 bisulfide of carbon in tight bins is by far the most satis- 

 factory means of protecting stored grain. In destroying 

 the insects, use one pound to one hundred bushels of 

 grain. 



Fig. 112. Grain moth 



