360 INSECTS AFFECTING VEGETATION 



gradual disappearance of so many of our feathered friends, and the 

 ignorance prevailing in regard to other animals, which are hunted 

 down and killed without mercy, although many of them are our 

 friends. The relation between our wild animals and agriculture has 

 not received that attention which it well deserves. Many animals 

 are considered the greatest enemies of man while in fact they are his 

 benefactors and deserve corresponding treatment. 



Many other methods might be enumerated by means of which 

 we can counteract the undue increase of noxious insects, but the 

 above list is sufficient to show that even without the use of poison and 

 machinery much can be done to protect our crops. But we must 

 always study the habits of our enemies, and thus become enabled to 

 select just the one remedy that promises to be effectual. In the war- 

 fare against noxious insects there is no royal road which can always 

 be followed. 



Introduction of Parasites and Cannibal Insects. This is also a 

 very promising remedy in some few and special cases. In a state of 

 nature the relationship between plants and insects is so nicely bal- 

 anced that each species has a number of checks which prevent undue 

 increase. But even there it sometimes happens that such checks be- 

 come ineffectual from disease or unfavorable climatic conditions, and 

 as a consequence devastations upon a large scale take place. But as a 

 very general rule the disturbed balance is soon restored to its equilib- 

 rium. When man imagines he can improve upon nature by adding, 

 purposely or otherwise, a new factor, or by removing one, most un- 

 expected results may follow. For instance the introduction of the 

 European rabbit into Australia was followed by such deep-rooted dis- 

 turbances between animals and plants that the whole Australian na- 

 tion is now forced to fight this animal to regain possession of the agri- 

 cultural products. The introduction of the English sparrow into the 

 United States is another example, and has already been of sufficient 

 influence to disturb the ancient order of things. So it is with the 

 accidental introduction of foreign noxious insects, as our farmers 

 have learned to their sorrow. As such recently introduced species 

 are usually not accompanied by their enemies these latter ought to be 

 introduced after careful consideration of the case in all its bearings. 



To the natural methods to prevent the undue increase of noxious 

 insects might be added proper laws. People unwilling to do their 

 share in preventing losses caused by insects ought to be forced by 

 carefully prepared laws to do their duty, if not to themselves, at least 

 to their neighbors and to the community at large. Insects that 

 threaten to become a serious danger to the inhabitants of a whole 

 state should be considered as a public calamity, like some contagious 

 disease, and should be suppressed by every known means. (Bui. 28, 

 Minn. Agr. Exp. Sta.) 



Barriers. Many plants may be protected at critical periods by 

 surrounding them by some obstacle which the threatening insect can- 

 not pass. Frames or boxes without tops or bottoms, covered with 

 mosquito netting above, are extensively used in some sections to pro- 

 tect the hills of young melon or cucumber vines from the attack of 



