Insects of Shade Trees and Their Control. 51 
bodied grubs hatch and begin eating away the underside of the leaf. 
When after several molts they are full grown, they partly cast the 
last skin and pupate in it fastened to the leaf. ‘“ Hangers” they 
are called in some sections of the country, where the beetles issuing 
from them are known as “hard shells.” During the growing sea- 
son the generations overlap, owing to more rapid development of some 
and slower growth of others, so that all stages, from egg to adult, | 
may be found at the same time. 
Remedy.—Spray with lead arsenate (p. 11), especially as soon as 
growth starts. Direct the spray against the underside of the leaves 
and for smooth leaves add soap (p. 14) so that the spray will stick 
to the leaves. 
LARGE ELM AND WILLOW SAWFLY.” 
How injurious—More commonly in the Middle West, and locally 
in the East, the large elm and willow sawfly has been observed com- 
pletely defoliating willow and elm trees and groves, and occasionally 
poplar and other trees. As stated in connection with other defoliating 
insects occurring in the Middle West, such outbreaks are pathetic in 
view of the solicitude with which trees are regarded there and the 
disappointment entailed when they are found undergoing despoliation. 
How recognized —Occasionally the tops of these trees look as if 
overrun by fire from the girdling of the bark of the twigs by the 
adult sawfly (fig. 32, 6). More often, however, their leaves are 
found blistered by eggs or larvee in pockets (fig. 32, a) or eaten by 
cylindrical, coiled, yellowish-white worms (fig. 32, e, e) with a black 
line down the middle of the back. 
Habits——The caterpillar-like insects that eat the leaves attain full 
growth about July or August and descend to the base of the tree 
where they spin a tough, coarse, silken cocoon (fig. 32, 7) among the 
débris or just below the surface of the ground and overwinter there. 
The following spring they change to pup (fig. 32, g, 2) and the 
adults, rather large, flylike insects, with four clear wings (fig. 32, 7), 
appear about May, mate, and the females make slits in the fleshy part 
of the leaves and thrust their eggs (fig. 32, ¢) into these pockets and 
from these the young worms (fig. 32, 7) come out to feed soon after 
hatching. 
27 Cimbex americana Leach, 
