THE SPRUCE INVESTIGATION. 255 



able conditions, prove quite serious enemies of the living tim- 

 ber. They are at least among the principal allies of the 

 destructive bark beetles in attacking trees in any way weak- 

 ened in vitality. One species of this class of borers 1 has, as I 

 have observed, caused the death of a great number of hemlock 

 trees, while another speoies 2 is killing the oak in different sec- 

 tions of the State; others attack and kill the broad-toothed 

 aspen, the common dogwood and willow; while the common, 

 flat-headed apple tree borer is destructive to fruit trees of vari- 

 ous kinds. They are, therefore, among the most destructive 

 insect enemies of trees. 



ROUND-HEADED SPRUCE BARK MINERS. 



The so-called round headed bark 

 miners, (See Fig. XXVIII,) as the name 

 indicates, are distinguished from the 

 flat headed kind by the round or cylindri- 

 cal form of the front segments of the 

 body which is also broader than other sig- 

 ments. They are the young of long-horned 

 or Longicorn bee- 

 llea, and theirW|vpp 



... ,, . . H>jyj(j::flr;ivw;S: : i^- 



habitS of mining -tyjMjpf 



Fig xxvii. T Round-head-through the inner PIg . xxvm.-Round headed 



ed wood miner: a-iult wood minpr^- thp ~ 



of the "Sawyer." bark and WOOd is terror & J 



the same as that of the flat-headed miners. As a rule, how- 

 ever, this class of round-headed borers mine in the bark until 

 they have attained sufficient size and strength to enter the 

 wood, when they are classed with the wood miners, but some 

 species live entirely in the inner bark and change to the 

 adult at the end of their burrows, either in -the inner or outer 

 bark. 



WOOD MINERS. 



The wood mining insects which infest different parts of the 

 spruce trees and saw logs, consist of adult beetles called tim- 



1 Meianophila fulvoguttata, Harr. 



2 Agrilus bilineatus, Web. 



