WHEAT-FLIES. 261 



a. The Hessian-fly (Cecidomyia destructor) ; b, Markwick -fly 

 (jChlorops pumilionis) magnilied. 



It now appears that Markwick was altogether mis- 

 taken in identifying his insect with the Hessian-fly 

 {Cecidomyia destructor, Say), which has been accu- 

 rately described by Mr. Say in the '' Journal of the 

 Academy of Natural Sciences of Philadelphia " for 

 1817. It is a little larger than our wheat-fly, more 

 slender in the body, has longer legs, and is not orange, 

 but black and fulvous. The female deposits from 

 one to eight or more eggs on a single plant of wheat, 

 between the sheath of the inner leaf and the stem 

 nearest the roots ; in which situation, with its head 

 towards the root or first joint, the young larva passes 

 the winter, eating into the stem, and causing it to 

 break.* 



The devastation committed by the Hessian-fly 

 seems to have been first observed in 1776, and it 

 was erroneously supposed that the insect was con- 

 veyed among straw by the Hessian troops from Ger- 

 many. It was first noticed in the wheat fields of 

 Long Island, from which it spread gradually at the 

 rate of fifteen or twenty miles round; and in 1789 it 

 had advanced two hundred miles from its original 

 station in Long Island. Other accounts state that it 

 did not travel more than seven miles annually, and 

 did little serious damage before 1788. Their num- 

 bers seem almost incredible. The houses in the 

 * Mag. Nat. Hist., vol. i. p. 228. 



q3 



