MAN'S ACCOUNT WITH THE LOWER ANIMALS 11 



preventive or remedial measures. We want to know all about 

 the circumstances under wHcli the insects can thrive, with a 

 view to storing our grain under conditions which make insect 

 Ufe impossible. We want to know what poisons can be 

 applied without injuring the grain for our own purposes. We 

 also want to learn as much as we can about the natural enemies 

 of the grain-pests, especially the hymenopterous parasites to 

 which I have referred, with a view to enlisting them, if possible, 

 in our service. 



There is a great variety of problems here, not only for the 

 zoologist but also for the chemist and the physicist acting in 

 co-operation with him. Some of them have already been more 

 or less satisfactorily solved. We know pretty well the Umits 

 of temperature within which grain-insects can thrive. We 

 know that they do not like cold and also that by heating the 

 grain to quite a moderate degree they may easily be exter- 

 minated. The best method of applying the heat is a problem 

 for the engineer, but it is successfully done in America on a 

 large scale, especially in mills, where it appears to be supplant- 

 ing the older methods of fumigation by means of carbon 

 bi-sulphide or other poisonous gases. We also know that a 

 certain degree of moisture in the grain is highly favourable 

 to the development of the pests, and that it is therefore 

 necessary that grain intended for storage should be sufficiently 

 well dried. 



All this is common knowledge and need not detain us. I 

 had intended, however, to give you an account of some 

 experiments which I myself have lately been making in this 

 connection and which have yielded some rather surprising 

 and interesting results, possibly of considerable practical 

 importance. Unfortunately I am advised that it may be 

 desirable to withhold publication of these results for the 

 time being, and therefore, much as I should Uke to take 

 you into my confidence, I am afraid that I must not do so. 



Illustrations of the economic importance of zoological in- 

 vestigations, analogous to the case which we have just been 

 considering, might be multiplied a thousandfold. I need only 



