PRACTICAL, TREATMENT — SCIENTIFIC TERMS. 21 



NUMBER MORE IMPORTANT THAN SIZE. 

 It is worthy of remark tliat by far the greater i)roi)ortion of the 

 damage caused by injurious insects is effected by si)ecies of very small 

 size, whilst the large species are generally harmless. The two most 

 serious fruit insects, the Oodling-moth and the Plum-curculio, are both 

 below the medium size, and the Apple bark-louse, the Apple-aphis, the 

 Hessian-fly, and the Wheat-midge, are so minute tliat they would not 

 be noticeable were it not for the wide destruction which they cause to 

 some of our most valuable crops, in consequence of their excessive mul- 

 tiplication. 



TREATMENT OF INJURIOUS INSECTS. 



For the details of treatment the reader is referred to the i)ractical 

 treatises and reports which have been published upon this subje(;t. We 

 can give here only an abstract of the methods to be pursued. 



First, hand-picking and destruction by machinery, as in the case of 

 the Colorado potato-beetle ; second, poisoning by such substances as 

 raris-green, hellebore, and carbolic acid, as in the cases of the Potato- 

 beetle, and the Currant saw-fly ; third, rendering their food distasteful 

 jind repugnant to them by the application of such substances as ashes, 

 liuie, and whale-oil soap, which are applicable to all foliage-eating in- 

 sects ; fourth, anticipating their attacks by planting at such times as 

 will cause the crops to sprout or to mature too early or too late for them, 

 both of which plans are exeraplitied by winter wheat, in its relation to 

 the Chinch-bug and the Hessian-fly; and fifth, when all other means 

 fail, preventing their ravages by abstaining for a year or two from rais- 

 ing the damaged crops. To these may be added, in certain favorable 

 instances, the transportation and colonization of friendly parasites. 

 An experiinent of this kind has been performed by the author by the 

 transportation from the central to the northern parts of the State of 

 Illinois, of the minute Chal.cis-fly, which is parasitic upon the Oyster- 

 shell Bark-louse. 



The above list exhibits the most common methods of contending with 

 injurious insects, and these methods admit of almost indeiitiite modifi- 

 cation. But they can be most usefully described in connection with the 

 particular species of insect to which they are respectively applicable. 



9 

 USE OF LEARNED AND SCIENTIFIC TERMS. 



With regard to the use of scientific terms^ derived mostly from the 

 Greek and Latin languages, it is to be remarked that though they may 

 appear diflicult and forbidding, at first sight, the student soon becomes 

 familiarized with them, and finds them to be almost indispensable by 

 enabling him often to express in one or two words what would require a 



