SHUCK PROTECTION FOR EAR CORN, 7 



Table IV. — Relation of the shuck covering of corn to the increase in weevil infestation 



during storage. 



Kind of shuck covering. 



Percentage of ears 

 infested. 



Increase 



or 

 decrease 

 during 

 storage. 



October, 

 1915. 



August, 

 1916. 



Poor 



52 

 38 

 9 



97 

 55 



4 



45 





17 





— 5 







Of the ears in poor shucks, 52 per cent were infested in 1915 and 97 

 per cent in 1916. The infestation in 1916 was 45 per cent greater 

 than in 1915. Of the ears in good shucks with wormholes, 38 per 

 cent were infested in 1915 and 55 per cent in 1916. The infestation 

 in 1916 was 17 per cent greater than in 1915. Of the ears in good 

 shucks without wormholes, 9 per cent were infested in 1915 and 4 per 

 cent in 1916. The infestation in 1916 was 5 per cent less than in 

 1915. 



It seems a significant fact that during the period of storage the per- 

 centage of weevil-infested ears increased decidedly in poor shucks 

 and in good shucks with wormholes, but there was no increase in the 

 percentage of ears infested in good shucks without wormholes. These 

 data, coupled with the fact that no evidence could be found showing 

 that weevils attempt to cut the shucks, indicate that the right kind 

 of shuck covering is an effective barrier to this class of insects. 



LABORATORY INVESTIGATIONS. 



It is probable that the insects in seeking their food follow the line of 

 least resistence. Under ordinary field and storage conditions they 

 naturally attack the ears with least protection first and successively 

 attack those with greater protection as the demand for food increases. 

 While the investigations discussed on the preceding pages show that 

 the better class of shuck protection successfully resisted insect damage 

 under existing conditions, it is natural to suppose that insects which 

 can eat the hardest kernels (fig. 3 ) of corn would also cut their way 

 through the protecting shucks if sufficiently urged by hunger. With 

 ordinary field and storage conditions it has always been possible 

 for weevils to find some food, and for this reason it was not necessary 

 to force a way to the corn in the best shucks in order that they might 

 avoid extinction. With complete success in the breeding of ideal 

 shuck coverings this last condition might arise, and it is desirable to 

 know whether the acquired shuck coverings would prevent infestation 

 under such conditions. To determine this point a number of weevils 

 were confined in properly ventilated jars with ears of com in good 

 shuck coverings, but with no other source of food. The test was 



