WILLOW SAW-FLY 



273 



The Willow Saw-fly. This large saw-fly (Cimbex americana 

 Leach) has a shining black head ; the body is steel blue, with three 

 or four elongated, oval, yellowish spots on each side. The wings 

 are smoky brown in color, and the legs bluish black with yellowish 

 feet. The well-known larvae, when full grown, are three-fourths 

 of an inch long, pale yellow or greenish hi color with a black stripe 

 along the middle of the back. The head is large, rounded, and as 

 wide as the body. When the saw-fly rests or is disturbed, it lies 

 on its side and rolls its body (Fig. 277), a habit which distinguishes 

 it from real caterpillars. 



Life History. The female fly deposits her eggs below the sur- 



FIG. 277. The willow saw-fly, caterpillar, adult, and open cocoon, d. Natural size. 



face of the leaf. The points where eggs are placed can be plainly 

 seen on the under surface, being bluer than the rest of the leaf, 

 and they become reddish with age. There may be from one to 

 nine eggs on a leaf. The larvae, after hatching, remain within this 

 blister-like structure for a time. In July and August they become 

 full grown; they then leave the foliage and are found in tough, 

 silken cocoons under the tree or shrub hi the ground just below 

 the surface. They remain in this condition over whiter and emerge 

 in spring. 



Injury and Control. Although this saw-fly destroys the 

 foliage of willows, poplars, and elms, and is recorded as attacking 

 maples, lindens, and alders, it is not considered injurious and is 

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