CHAPTER XII 

 INSECTS AFFECTING FIELD CROPS AND PASTURAGE 



THE enormous amount of grain and other field crops raised in 

 this country, and the importance of stock-raising and milk produc- 

 tion, are such as to make consideration of insects affecting field 

 crops and pasturage of special importance. The pests concerned 

 are discussed in the following pages. 



WHEAT INSECTS 



Hessian Fly (Mayetiola destructor Say). This fly, which 

 causes an annual loss of many thousands of dollars in the United 

 States, is hardly ever observed by 

 the layman on account of its ex- 

 tremely small size. It is a dark- 

 colored gnat with two wings. As 

 it is only one-tenth of an inch long 

 (Fig. 204), probably not one in a 

 thousand of our farmers has ever 

 seen this insect in the adult stage. 



Life History. The so-called 

 "flaxseeds" (Fig. 205) which repre- 

 sent the pupal stage are easily ob- 

 served under the sheathing leaves, 

 next to the stem, generally above 

 the first joint, although they may 

 be found higher up on the stem. 

 The fly emerges from these flax- 

 seeds either in the stubble or in the 

 grass or weeds along the edges of 

 the fields. It lays from one hundred 



to One hundred and fifty eggS in FIG. 204. Hessian fly on wheat plant, 



much enlarged. 



early spring on young wheat plants. 



The maggots hatching from these eggs work against the stem 

 beneath the sheath leaf as above indicated. The winter is passed 

 in the pupal stage; called "flaxseed" because of its resem- 

 blance to the seed of the flax plant. 



Injury. Affected plants, when young, appear darker than 



185 



