226 



SCHOOL ENTOMOLOGY 



by the females through any openings caused by drying and 

 splitting, or are laid loosely among the shelled beans. The 

 larva feeds within the bean and becomes a fat footless grub 

 as shown in the illustration. The pupal stage is also passed 

 within the bean. Experiments have shown that the com- 

 plete life cycle may require from twenty-one to eighty days, 

 according to the temperature. Probably about six genera- 

 tions occur annually in the latitude of the District of Colum- 

 bia, and fewer farther north. A number of weevils may 



FIG. 157. The common bean-weevil (Bruchus obtectus Say). 

 Chittenden, U. S. Dept. Agr.) 



a, beetle; b, larva; c, pupa all greatly enlarged. 



(After 



infest a single bean. Weevily seed should never be planted 

 as but a small percentage will germinate. Infested seed 

 may be thrown lightly into water, when that badly infested 

 will float and can be destroyed. 



Either heat or fumigation as advised for the pea-weevil 

 will be effective, except that it is useless to hold the seeds 

 over, as this species breeds in the stored seed. 



134. Grain-weevils and Grain-beetles (45). The term 

 "weevil" is commonly applied to almost any insect affecting 

 stored grain, but it should be used only for the true snout- 



