112 PHYSIOLOGY AND NATIONAL NEEDS 



web which they sometimes spin over the heaps of 

 grain, it being asserted that the grain under such 

 a web is always in good condition. However this 

 may be, there can be no doubt, not only that the 

 larvae actually do a certain amount of damage to 

 the grain itself, but also that their presence in 

 a warehouse must be a source of danger to other 

 food products stored in the same or adjacent 

 buildings. In the case which we investigated, where 

 hundreds of thousands of " maggots " were crawling 

 over the grain and the adjacent woodwork, we found 

 that the moth of whiph they were the larvae, and 

 which was also to be found in the granary in the 

 adult state, was the notorious Ephestia elutella, 

 which is known to infest almost any kind of food 

 substance, from grain to chocolate. Here was a 

 breeding-ground from which the insects might 

 spread in thousands over a large area, with disas- 

 trous consequences, and this danger was apparently 

 quite unrecognised by those in charge. 



Unfortunately time does not permit of my saying 

 much about the habits and life-histories of the 

 various grain insects, but we may pause for a moment 

 to consider their effect upon the grain. Let us 

 confine our attention to the weevils. The amount 

 of damage which these little creatures do is of 

 course directly proportional to their numbers, and 

 these depend upon their rate of multiplication. We 

 have made more than 90 experiments to determine 



