THE PRINCIPAL INSECTICIDES. 21 



Tobacco is a very valuable insecticide for use 

 against vermin on domestic animals, and green-house 

 pests. It may be used in the form of a decoction, a 

 smoke, or dry. The refuse stems and powders from 

 the cigar factories are very valuable as insecticides 

 and fertilizers, and frequently, in the middle west- 

 ern states, they may be obtained for little or nothing. 



Bisulphide of Carbon, is a volatile substance used 

 for destroying grain insects, ants, the Grape Phyllox- 

 era, and other insects which may be reached by a 

 vapor. It is inflammable and should never be used 

 in the vicinity of a fire. 



Benzine is another volatile substance used for much 

 the same purposes as the last. 



Gasoline may also be mentioned in the same con- 

 nection. 



Coal Tar has been largely used in the west for de- 

 stroying Rocky Mountain Locusts, being placed on 

 flat pans, on which the insects jump and are caught. 

 It is also employed to prevent the migrations of the 

 Chinch Bug. A shallow V-shaped channel is made 

 with the corner of a hoe along the borders of the 

 field to be protected, and tar poured in. So long as 

 the tar does not dry out, the immature Chinch Bugs 

 cannot cross it. 



APPLYING INSECTICIDES. 



The methods of applying insecticides, of course, 

 vary according to the nature of the substance, and 

 the insect against which it is to be used. The 



