THE HESSIAN-FLY ? 433 



The fly producing this destructive grub is not quite 

 the fourth part of an inch in length. Its thorax 

 is dark-coloured, but marked longitudinally with 

 two yellow lines. The grubs are white, about two 

 lines in length, composed of ten rings, with the 

 head pointed at the end. The chrysalis is yellow* 

 shining, rather more than one line long, and com- 

 posed of rings. 



In order to determine the species of this animal, 

 Mr. Mark wick planted some diseased roots of wheat 

 in a small flower-pot filled with bran : this pot he co- 

 vered over with gauze, in such a manner that no in- 

 sect could get in from the outside, nor could any 

 escape from within. Not very long afterward he 

 discovered three small flies, which he found to be 

 of this species, sitting on the inside of the gauze, 

 and a few days after three more. There were in 

 the pot six roots of diseased wheat, which thus pro- 

 duced six flies. On examining the roots, he now 

 iound an empty chrysalis in each. 



The principal stems of the corn being entirely 

 destroyed by this grub, gave the crop of wheat be- 

 longing to a friend of Mr. Markvvick so disastrous 

 an appearance that scarcely a hope was entertained 

 of any produce : but after the grub had changed into 

 its chrysalis state the mischief ceased, and none of 

 the roots were so materially injured as to prevent 

 them throwing out shoots on each side. At harvest- 

 time it was a matter of most agreeable surprise that 

 this should prove a good crop of wheat, with the 

 ears throughout the field large and well filled. The 

 owner even thought it the best crop on his farm, 



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