INSECTS AND PREVENTIVES 



tributed, from which it escapes gradually into the 

 nozzle of the bellows when operated. It is made 

 in various patterns and sizes, all operating in sub- 

 stantially the same way. 'There are other imple- 

 ments that can be used, but they are of inferior 

 efficiency, and have nothing to recommend them 

 except in being sold at a lower price. The best, 

 in this as in many other things, will be found the 

 cheapest. 



Changing the crop affords a partial preventive 

 against the inroads of insects, providing that the 

 change is to an entirely different family of plants; 

 for it is well known that the continued cultivation 

 in one locality of any particular crop has a ten- 

 dency to assemble there all its peculiar enemies, 

 and favours their rapid multiplication. 



No absolutely complete preventives are known; 

 and cultivators must recognize the necessity of 

 constant exertion, and unremitting use of the best- 

 known and most efficient of those now in use. Due 

 inquiry and fuller knowledge of facts might help to 

 accomplish much toward limiting, if not wholly 

 exterminating, each and every kind of pestiferous 

 insect. Neighbours should combine, both for 

 observation and action; first to devise, and then 



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