BULLETIN 708, U. S. DEPARTMENT OF AGRICULTUEE. 



much less important as a means of protection. Fortunately, this 

 did not appear to be the case, as is shown by the data given in 

 Table III. - ' 



Table III. — Relative amount of damage done to corn by weevils and by beetles. 





Total 

 number 

 of ears. 



Tercentage of— 



Infestation. 



Ears with 

 damaged 

 kernels. 



Damaged 

 kernels. 



Weevils and beetles together 



Beetles alone 



135 



60 



100 

 5 



60 to 75 

 Trace. 







From 60 to 75 per cent of all the kernels on the 135 ears infested 

 with weevils and beetles together were seriously damaged. Of the 

 60 ears infested with beetles alone, 5 per cent were damaged by 

 something. It is possible that worms or other insects not present 

 at the time of the examination might have been the cause of this 

 damage. At any rate the damage amounted to a mere trace on 11 

 kernels. It is evident, therefore, that the beetles when alone were of 

 no practical importance in the corn studied. The 11 kernels whose 

 damage is in question were softer than most of those in the varieties 

 used in these studies. If the beetles did this damage, then it is 

 probable that they did so because the comparative softness made it 

 possible. Other investigations have shown that some of the com- 

 paratively soft-grain varieties of corn from outside the areas that are 

 badly infested with grain insects may be directly damaged by beetles. 

 This again suggests that kernel density may determine whether 

 direct damage from beetles is possible, and emphasizes the importance 

 of using adapted corn which may involve protective factors that 

 have not yet been clearly recognized. Because of the importance 

 of adapted varieties for practical purposes this publication is confined 

 to the results with such varieties, and since the beetles were not an 

 important damaging factor in this connection, these insects are not 

 further considered here. 



The lots of corn considered in Tables I and II were grown in the 

 same plat and harvested at the same time, and were as comparable 

 as it is possible for two lots of ears to be under similar circumstances. 

 As the lot considered in Table I was examined for infestation at 

 harvest time (October, 1915), and the lot considered in Table II was 

 examined for infestation after about 10 months in storage (August, 

 1916), the differences between the percentages of infestation found at 

 the time of examination should represent the gain in infestation 

 during storage. The percentages of weevil infestation shown in 

 Tables I and II are compared in Table IV. 



