184 
This, I think, is beyond doubt, true, not only with reference to this 
species, but also to many others. 
The wooly aphis of the apple tree, as I have repeatedly noticed, 
appears to attack defective, injured or unhealthy trees in preference 
to those which are sound and vigorous. Where these insects attack 
vigorous and healthy plants, they prefer those in close, confined situa¬ 
tion, than those amply supplied with sun and air. This fact therefore 
suggests as a remedy proper pruning in the case of trees and proper 
exposure to sun and air of the smaller plants. 
Some years ago a machine was invented in Paris for the purpose of 
forcing through a tube by. means of a kind of pump, the fumes of 
tobacco, sulphur, etc., upon the infested portions of plants. I sug¬ 
gested the use of an apparatus of this kind in an article to the Prairie 
Farmer without then being aware that it had ever been tried. What 
success has attended the use of this apparatus I am unable to state, 
but it certainly is worthy of a fair trial. Some tender plants as a 
matter of course, will not bear such treatment, but the larger number 
will; and as it is not necessary to limit the application to tobacco or 
sulphur, various other materials might be tried. 
