The Aspen Borer and How to Control It. 9 
Counts made on several areas show an average of about 25 per cent 
of the borer eggs destroyed by this insect. 
Two-winged flies parasitic on the borer grubs were found to de- 
stroy 5 per cent of them; predacious insects and birds, less than 1 
per cent. Fungous disease destroys 2 per cent of the mature larve, 
pupe, and immature adults. The total annual mortality of the 
borer from these causes is from 30 to 38 per cent. 
Fic. 6.—Living aspen, Cheyenne Mountain, Colo., altitude 
7,000 feet. This tree is infested by 2 and 3 year old 
larve of the aspen borer. The swelling on the main 
trunk are the result of the work of these larve, 
ASSOCIATED INSECTS AND DISEASE. 
Generally associated with the injury of the aspen borer, there are 
the following insects and a fungous disease which more or less hasten 
the deterioration of the trees. 
The bronze birch borer? attacks healthy, injured, and dying trees; 
it precedes and follows the attack of the aspen borer and may cause 
the death of the tree. 
A flat-headed borer * deposits its eggs in the egg scars of the aspen 
borer, and in ax marks and bruises, and extends the damage in the 
heartwood. 
7 Agrilus anvius Gory. § Poecilonota cyanipes Say. 
