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 rest, 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 bursts 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 



