Insects of Shade Trees and Their Control. 55 
by injecting carbon disulphid (p. 14) into the holes and promptly 
plugging them with clay, putty, or similar substance. Where facili- 
ties are at hand the trunk and larger branches of the trees may be 
sprayed in the late summer with poisoned kerosene emulsion (p. 12- 
13) or miscible oil (p. 12), which will reach and kill the borers that 
have just penetrated the bark. Care should be taken to avoid spray- 
ing the foliage, as this is injured by these solutions. 
ELM BORER.” 
Signs of attack—Elm trees only are subject to injury by this 
borer. The leaves of tops or ends of branches of infested trees turn’ 
brown and fall in summer, after which tops and branches here and 
there die, as shown by their failure to leaf out in the spring, and in 
two or three years the entire tree is killed. Thorough search of the 
trunk and larger branches of dying trees discloses patches of dead, 
readily peeling bark with burrowing roundheaded grubs beneath it 
(fig. 834, 7). This is the form of the insect that does the injury, and 
when the limb or tree is girdled by the burrows (fig. 34, 3) its doom 
is sealed. 
flow destructive——Trees growing in unfavorable environment, 
particularly in cities, are most subject to attack by this borer, and 
then apparently only when the trees have been previously weakened 
by some other agency. Hence it becomes epidemic only occasionally, 
but on such occasions it is apt to wipe out the trees on entire blocks 
of some communities. 
Distribution —The elm borer probably occurs generally through- 
out the northeastern United States. 
Description and seasonal history—The parent insect is a gray, 
long-horned beetle (fig. 34, 4), about one-half inch long and marked 
with red lines and black spots. Its flying period is between May 
and August. At that time the eggs are laid singly or in groups on the 
bark, where they hatch into tiny, footless grubs which promptly 
funnel through it to the cambium layer. Here they excavate con- 
tinuously wider cavities to accommodate them as they grow. These 
tunnels, when they reach around the tree or limb, girdle and kill. 
The full-grown grub (fig. 34, 7a) is white, a little over an inch in 
length, thickest in front, but the head is only about half as wide 
as the segment immediately behind it. It is not definitely known 
how long the insect remains in the grub stage, but on reaching full 
erowth it cuts out a cell beneath the bark and pupates in it, looking 
very much like a mummified beetle (fig. 34,2). In the spring, about 
May, these pupx change to adult beetles which cut round holes in the 
bark and come out. 
29 Saperda tridentata Oliv. 
