DIPTERA OK TRUE FLIES. 199 



second node from the ground. Here these little white larvae 

 feed upon the sap of the plant, and turn to the curious " flax- 

 seed " stage, in which the larva remains in its brown skin, which 

 has hardened to form the puparium, and which resembles a flax- 

 seed in appearance. The larvae are at times pale green, at 

 others tinted with red. 

 In these flax-seeds the 

 larva turns to a minute 

 pale -brown pupa. These 

 flax-seeds may remain as 

 such all the winter, or „ „, „ 



' Fig. 95. — Wing of Cecidomyia. 



they may give rise to a 



second brood of flies. This second brood hatches out in Sep- 

 tember, long before our wheat is up, and thus have to lay 

 their eggs on other plants, such as couch grass and timothy 

 grass, pupating there in the spring, and then give rise to the 

 May brood. The presence of this pest in a field is very marked. 

 The straw, as soon as the ear begins to develop, bends over 

 above the second node, and looks as if weather-beaten, the grain 

 being small, if not spoilt. In America the second brood lays its 

 eggs on the young winter wheat, the lai*v8B living in the crown 

 of the plant just beneath the ground, and causing the leaves to 

 present an unhealthy dark and broad appearance, the central 

 leaf usually disappearing. It is this method of attack that is the 

 most severe, whole strips of wheat being entirely killed by it ; 

 but for obvious reasons we cannot suffer from this form of 

 attack on our side of the Atlantic. The Hessian fly is most 

 prevalent in the eastern counties of England, but may be found 

 aU over the south, west, and in Yorkshire, &c. A second brood 

 is the exception here, the insect passing the winter in the flax- 

 seed stage, which remains very often, if the corn is not cut 

 close, in the " gratten." Ifumbers may also be seen in the cav- 

 ings and screenings from the threshing-machine. Wheat, barley, 

 and rye, as well as the wild grasses mentioned, are attacked, but 

 never oats. 



