THE DAVEY INSTITUTE OF TREE SURGERY 
ing trees tend to drown out the larve before they penetrate the 
bark, and are consequently less subject to attack. 
6. ELM BORER 
Family CERAMBYCID. Species Saperda tridentata Olivier 
76. This is another native Saperda, and probably does not at- 
tack the trees until they are weakened through some other cause or 
agency. They become very abundant in certain localities from 
time to time, and kill many magnificent elms by undermining the 
bark and cutting off the food supply, thus causing the bark to 
separate from the wood in large flakes. 
77. The elm borer has been known in the literature as Comp- 
sidia tridentata, Compsidia tridentata var. dubiosa, and as Saperda 
trilineata. 
78. Itis generally associated in its destructive work with three 
other borers, the reddish elm snout beetle, 
Magdalis armicolis Say; the black elm snout 
beetle, Magdalis barbita Say, and the Amer- 
ican elm borer, Neoclytus erythrocephalus 
Fabr. The elm borer is probably the primary 
cause of the injury, as it is found in the liv- 
ing tissues, while the others are found in the 
dead or dying tissues. 
79. These borers work just under the 
bark, making irregular burrows which, if 
abundant, eventually girdle the trunk or 
limbs. The work is done so secretly that 
frequently their presence is not suspected 
until the trees are beyond hope. 
80. The life history of the elm borer has 
never been carefully worked out, but it is 
probably the same as the life history of the 
other Saperdas, requiring two or three years 
for the larva to mature. The larva is a 
typical round-headed borer, a little over an | dadenaal ‘illiias 
inch in length when full grown. The beetle Courtesy Iinois State 
is of a grayish color, with a reddish margin Fig. 7 
tothe thorax and a red stripe-near the outer E4yy borer enlarged, 
edge of each wing cover, and three teeth of After S. A. Forbes. 
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