ON THE CECIDOMYIA DESTRUCTOR, OR HESSIAN FLY. 51 



handful of straws, torn up by the roots, and in every instance the pupa was 

 either in the old grain or the root. 



Within a week from the time of these observations the wheat was reaped, 

 but the pupa in the stubble was not perfected until August. 



In the spring of 1838 I detected the larva in a field that had been sown early 

 in the previous fall; it was always in the centre of the culm, there being from 

 one to six in the same stalk, at various distances, from the root to the third 

 joint. It had a pale, greenish- white, semitransparent appearance; in form 

 bearing some resemblance to the silk-worm. I regret that I made no drawings 

 or notes at the time ; this description, therefore, is from memory. The upward 

 path of the worm was distinctly marked. The perfect fly appeared in June. 



In the fall of 1837, Mr. Kirk, a farmer of Bucks County, procured Mediter- 

 ranean wheat, which yielded an abundant crop, free from the Hessian Fly. 

 The seed from this wheat was sown in the fall of 1838. In the spring follow- 

 ing he detected the larva thinly scattered in the resulting crop ; but the grain 

 of the present year, 1840, from the same stock, has been greatly injured by 

 flies from neighbouring fields, planted with American wheat. 



From these facts I have been confirmed in my first impression, that the egg 

 is deposited in the grain, remains dormant until the grain vegetates, is then 

 hatched in or near the grain, lives in the centre of the culm, and mounts with 

 the growing stalk. 



Should the egg be hatched in the fall, the slow growth of the wheat allows 

 the insect to penetrate into every shoot, and rise with the growing straw, but 

 if it be retarded until spring, the uninfected shoots grow rapidly, while those 

 containing the larva become sickly and abortive; hence the difference in the 

 position of those found in the wheat vegetating in the fall, and those not ap- 

 pearing until spring. 



Various experiments have been tried to destroy the egg in the grain, but the 

 vital principle appears so carefully guarded in insects' eggs, that whatever de^ 

 stroys life injures the grain. The only remedy, then, is to procure seed from 

 an uninfected district. 



Note. — In Susquehanna and Bradford counties the Hessian Fly has never yet made its ap- 

 pearance. 



