THE ELM SAW-FLY. 
519 
hook, curved inwards. He often measures an inch in 
length, and his wings expand about two inches. 
These insects appear from the latter part of May to the 
middle of June, during which period the female lays her 
eggs upon the common American elm, 
the leaves whereof are the food of her 
young. (Fig. 243, larva.) The latter 
come to their growth in August, and 
then measure from one inch and a half 
to two inches in length. They are 
rather thick, and nearly cylindrical in 
form, and have twenty-two legs, or a pair to every ring 
except the fourth. They have a firm, rough skin, of a 
pale greenish yellow color, covered with numerous trans- 
verse wrinkles, with a black stripe, consisting of two nar- 
row black lines, along the top of the back, from the head 
to the tail ; and their spiracles, or breathing-holes, are also 
black. When at x’est, they lie on their sides, curled up 
in a spiral form, and in this position look not much unlike 
some kinds of cockle or snail shells. 
Like all the false caterpillars of the genus Cimbex, this 
insect, when handled or disturbed, betrays its fears or its 
displeasure by spirting out a watery fluid from certain little 
pores situated on the sides of its body just above its spira- 
cles. After its feeding state is over, it crawls down from 
the tree to the ground, and conceals itself under fallen 
leaves or other rubbish, and there makes an oblong oval, 
brown cocoon (Plate VIII. Fig. 11), very closely woven, 
as tough as parchment, and about an inch in length. In 
this the false caterpillar remains unchanged throughout 
the winter, and is not transformed to a chrysalis till the 
following spring. At length the insect hursts its chrysalis 
skin, and, by pushing against the end of its cocoon, forces 
off a little circular piece like a lid, and through the open- 
ing thus made it comes forth in its winged form. 
For some years past many of the fir-trees, cultivated for 
Fig. 243. 
