YALE AGRICULTURAL LECTURES. 23 



tions by insects are not noticed, because so insidiously made, 

 but if our eyes could but be opened to the activity of our little 

 foes, consternation would seize us. Go into our forests and we 

 see every portion of our trees attacked by some insect trunk, 

 bark, leaves, and roots, all having their peculiar depredators. 

 The sweeping away of our forests compels the insects which 

 formerly fed upon them to turn to the orchards, which have 

 replaced the forests. Thus we have the apple-tree borer, which 

 originally subsisted in the wild thorn-apple ; and the Buprestis, 

 from the oak ; and from present indications it is probable we 

 shall hereafter see the branches of our apple-trees lopped off 

 as are the limbs of the common red oak in particular years, and 

 by the same insect, the " oak-pruner." But in addition to these 

 native species, quite a number of foreign insects have been 

 imported in the thousand commodities, and in the numberless 

 trees and plants which we import, and these have proved the 

 most pernicious foes to our crops and trees. Our crops and 

 climate favoring their development, they multiply to a frightful 

 extent, and do far greater damage here than they did in Europe. 

 The bark louse, for instance, on both sides of Lake Michigan, 

 has ruined nearly every orchard. For years after the settle 

 ment of this country Avheat was an absolutely sure crop, but 

 the yield dwindled with successive years, and now, in large 

 districts, its culture is necessarily abandoned. Reasons have 

 been urged to account for this ; that our soil has deteriorated, 

 and our climate changed, but they do not explain the difficulty. 

 With the best of manuring and tillage, we cannot get the crops 

 our ancestors did with shiftless farming ; and even where new 

 woodland is cleared, and wheat is put into the virgin soil, the 

 crop is iniinitesimally small. The true cause is to be found in 

 the attacks of insects, and nothing else. The wheat midge and 

 the Hessian fly are the only insects which have attracted much 

 notice, and it is hence currently supposed that these are the 

 only important depredators which we have in our wheat fields. 

 But, a few years since, on coming to examine the growing 



