INSECTS INJURIOUS TO SMALL GRAINS 131 



following year. This is clone by cutting the straw circularly 

 on the inside, nearly severing it a short distance, varying from 

 one-half to one-inch, from the ground. If the wheat were grow- 

 ing wild, the winter winds would cause the stalk to break at 

 this point; and thus the insect after it had reached the adult 

 state could easily escape; while but for this cut it would be very 

 liable to be imprisoned in the straw." Ordinarily, the straw is 

 cut by the reaper before it becomes broken; but a strong wind 



FIG. 95, The western grass-stem saw-fly (Cephus occidenlalis) : a, larva; 

 b, female saw-fly; _c, grass-stem showing work, c, enlarged, a, b, more 

 enlarged. (After Marlatt, U. S. Dept. Agr.) 



just before harvest will cause a large number of stalks to become 

 broken, much as if affected by the Hessian fly. 



" After the circular cut has been made, the larva fills the 

 cavity of the straw just below it for a short distance with a plug 

 of borings. Between this plug and the lower end of the cavity 

 of the straw there is a place about one-half an inch in length. 

 It is here that the insect passes the winter." This cell is lined 

 with silk so as to form a warm cocoon. Here the larva passes 

 the winter and changes to a pupa in March or April. The adult 

 insect emerges early in May. The adults are four-winged insects, 



