10 



tion. They may be divided roughly into three groups, 

 according to the part of the tree they attack, as follows : 

 (1) Leaf insects, (2) trunk and branch-mining insects, 

 and (3) root-infesting insects. 



Tlie first group of the three includes most of the 



species which attract gen- 

 eral attention, though it 

 cannot be said that they 

 are the most destructive. 

 To it belong the fall web- 

 worm, the walnut-worm, 

 and the elm leaf-beetle so 

 destructive in the eastern 

 states. To it also belongs 

 /the Gypsy-moth, for the 

 destruction of which the 

 State of Massachusetts dur- 

 ing the three years ending 

 December 31, 1893, ex- 

 pended $175,000. Such 

 insects attract attention at 

 once from the nature of 

 their injury, the unsightly 

 appearance due to gnawed 

 leaves, webbing, and refuse, 

 taking away at once from 

 trees their practical value, 



as shade, and their esthetic 

 Fig. .3. Showinsr a marginal gall 

 produced by mites on black gum. value, as ornament. 



While their injuries are not at first so apparent, the 

 -work of the boring and mining species is not less injur- 

 ious, and is the more to be feared because its results are 

 not seen until the mischief under the bark is at an 

 advanced stage. The locust borer and the elm bark- 

 beetle are members of this group, both species being 



