HESSIAN FLY 257 



winter wheat. In spring wheat regions the flies appear 

 at about the time of the coming up of the wheat and deposit 

 eggs on it. There is not necessarily much (Hfl'erence in the 

 time and method of deposition except that those on winter 

 wheat are apt to be a httle higher on the stems and farther 

 from the ground. Tliese burrow into the stem in such a 

 way as to cause weakening of the stalk, which is apt to bend 



Fiu. 2U0.— The Hessian Hy: iidult mule— much enlarged. (After 

 Marlatt, Div. Ent., U. S. Dci)t. Ag.) 



and break as it approaches maturity and falls to the grountl, 

 so that it cannot be harvested. Sometimes only 1 or 2 per 

 cent, of the field will be infested and in other fields one-third 

 or one-half of the crop will be lost. As the wheat matures 

 the larvse mature and change to the flaxseed stage and 

 remain protected between the sheath and the stem of the 

 plants down near the ground. Sometimes they are high 

 17 



