cracks and crevices in the bark, mostly on unshaded parts of the 
tree. Young larvae bore directly through the bark to the cam- 
bium area. There they excavate galleries between the bark and 
wood, with occasional side trips into the xylem to molt and then 
to spend the winter. The galleries wind back and forth, usually 
across the grain of the wood. Mature larvae construct oblong cells 
in the wood or thick bark in which they spend the winter and 
pupate in the spring. Larvae of all sizes and ages have been found 
in infested trees during the winter, but the only ones capable of 
developing to adults were those which became mature before 
winter set in and were later subjected to sub-freezing tempera- 
tures. In the North, 2 years are required to complete the life 
cycle; in the South there is one generation per year. Barter (34) 
reported on the biology of the bronze birch borer in New 
Brunswick. 
The bronze birch borer prefers weakened or injured trees 
(471). Damage may be extremely severe in stands of such trees. 
Weakened residual trees following logging and individual shade 
and ornamental trees weakened by drought or other factors are 
often seriously injured. During the past several years, enormous 
volumes of birch suffering from ‘die back’’ were killed in the 
Northeastern States and Canada. In Canada, at least 1 million 
cords were killed during 1939 alone (108). The most effective 
control measures are those designed to promote and maintain 
host vigor. 
The bronze poplar borer, Agrilus liragus B. & B., breeds in 
poplar in Canada and southward in the United States to Pennsyl- 
vania and Arizona. Adults are blackish with deep green reflec- 
tions and are about 7 to 12 mm. long. Overmature or defective 
trees and young trees suddenly released by the removal of domi- 
nant trees are most often attacked; however, felled, topped, or 
girdled trees and trees damaged by Saperda calcarata and Hy- 
poxylon canker are also attractive. Infestations in standing trees 
usually begin in the crown and move downward. 
Adults are present during a period of several weeks during the 
Summer and feed on the leaves of poplar. Eggs are deposited in 
bark crevices and the larvae feed in the cambial region, excavat- 
ing long tunnels that zigzag back and forth in a compact manner. 
The larvae feed for two seasons in Ontario before becoming ma- 
ture (35). Woodpeckers took heavy tolls of mature larvae, pupae, 
and, presumably, adults in standing trees in Ontario. 
Agrilus horni Kerr occurs in Ontario and the northern tier of 
Eastern States, and breeds in young, apparently healthy aspen 
suckers, especially quaking aspen, some of which it girdles and 
kills. Adults are almost identical to those of the bronze birch 
borer except for shorter ovipositors in the females. 
Eggs are deposited on the smooth bark at the base of aspen 
suckers. The larvae bore into the bark and tunnel downward 
and out along large roots, gradually working their way through 
the bark to the cambium region. Once here, they turn around and 
tunnel back toward the main stem, making spiral galleries which 
encircle the roots and which may be continued up the trunk for 
several inches. Pupation takes place in a cell in the center of the 
stem, and the life cycle requires two years. Damage appears to 
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