GRAIN CONSERVATION 115 



may remain aHve for a long time in dry wheat, 

 ready to resume a more vigorous existence when the 

 necessary moisture is forthcoming. 



The effect upon the wheat of a large number of 

 weevils living under favourable conditions is very 

 remarkable. The adult females lay their eggs in 

 small punctures in the grains. The young larvae, 

 hatching from these eggs, bore their way deeply into 

 the grains, and there undergo their complete develop- 

 ment, gradually hollowing out the grain as they 

 feed, and finally eating their way out as perfect 

 insects. The adult lives for a long time and feeds 

 voraciously, and the combined efforts of adults and 

 larvae rapidly destroy the grain. In addition to 

 this direct effect there is an indirect one, which, 

 at any rate in a moist atmosphere, may be of great 

 importance in completing the work of destruction. 

 As they feed, the weevils produce large quantities 

 of excrement, and not only does this foul the grain 

 but it appears to attract large quantities of moisture 

 and forms a substratum for the growth of moulds — 

 and doubtless also of bacteria — by the action of 

 which the remainder of the grain is presently con- 

 verted into a black, decaying mass, resembling old 

 stable manure and giving off large quantities of 

 ammonia. In spite of the presence of the ammonia 

 weevils continue to live in the upper and less affected 

 layers of such a sample for a very long time. 



You may perhaps say : '' It's all very well to 



