10 Farmers’: Bulletin 1154. 
Another flat-headed borer® attacks injured and dying trees. It 
deposits eggs in old egg scars made by the aspen borer and in other 
injuries, and it bores into the heartwood. 
A large moth? which attacks the poplar and deposits its eggs 
in the borer egg scars is most frequently found in trees infested by 
“poplar borers. Its altitudinal range is the same as that of the borer 
none having been found above 9,000 feet. 
A pinhole borer" attacks injured and dying trees in which the 
sap has begun to sour. It follows the attack of the aspen borer and 
is found also in trees otherwise injured. 
Fig. 7.—Side view Fie. 8.—Side view Fig. 9.—Aspen borer: 
of larva of the of pupa of the Adult female, from 
aspen borer. aspen borer, side and from above. 
A roundheaded borer * which occurs at higher altitudes than the 
poplar borer is the chief depredator in the aspen. Large areas have 
been denuded as the result of its work. 
A heart rot,'® causing much deterioration and decay in aspen, fol- 
lows the attack of the aspen borer and other wood-boring insects, 
gaining entrance through the wounds made by them. It is present 
in nearly all trees attacked by the aspen borer. 
CONDITION OF TREES ATTACKED. 
Living, healthy, and injured trees are attacked by the aspen 
borer. Dead trees are never attacked. A strong preference is shown 
for trees which have partially succumbed to former attacks. 
® Dicerca prolongata, Lee. 1 Yyloterus sp. 18 Fomes igniarius, 
10 Cossus Sp. 1 Xylotrechus obliteratus Lee, 
