112 INSECTS INJUKIOUS TO STAPLE CROPS. 



larv^, but more rounded, being only one-sixth of aji inch 

 long, and reveal the legs and wing-cases of the imago 

 forming within tliem. The external case of the pupa, 

 called the puparium, is merely the shrunken and hardened 

 cast skin of the last larval stage, within which the insect 



Fig. 64. — Wheat Bulb-worm {Meromyza amerkana) a, mature fly; 

 b, larva; c, puparium; d. infested wheat-stem — all enlarged ex- 

 cept d. (After Marlatt, U. S. Dept. Agr. ) 



transforms to the pupa. The fly is abotit one-fifth of an 

 inch long. It is of a yellowish- white color with a black 

 spot on the top of the head, three broad black stripes on 

 the thorax, and three on the abdomen, which are often 

 interrupted at the sutures, so that they form distinct spots. 

 The eyes are a bright green. 



The winter is passed by the larva3 in the young plants, 

 and in spring they transform to pupae and adult flies. 

 These in turn deposit eggs in such a position that the 

 maggots issuing from them may readily feed upon the 



