200 DIPTEUA OR TRUE FLIES. 



Prevention and Remedies. — In those areas where G. destructor 

 is very abundant it is well to use the stouter-strawed varieties of 

 corn, and to burn the stubble after an attack by firing the 

 borders of the fields. All infested screening should be destroyed, 

 and light grain, which may often contain the flax-seeds as well, 

 given to stock. The Hessian fly is subject to a number of 

 Ichneumon enemies. In 1888 Mr Enock bred from 1694 flax- 

 seeds 58 more parasites than flies. 



The Wheat ^NIidge (Diplosis tritici). 



The Wheat Midge is very prevalent in England, and causes 

 persistent loss in corn-growing districts, although a small fly. 

 It is about the same size as the Hessian fly, but more deli- 

 cate in structure, and yellow or orange in colour, except the 

 eyes, which are black. It belongs to another genus, Diplosis, 

 whose characteristic wing venation is given in fig. 96. The 



female fly has quite a 

 long ovipositor, and may 

 often be seen in the 

 fields in clouds, flying 

 about low down amongst 

 Fro, 96.-WING OF Dipi.osis. ^'^<^ stalks close to the 



ground in the daytime, 

 when disturbed, but at sunset they come up to the ears to 

 deposit their eggs in the florets of the wheat. The larvse are 

 yellowish-red in colour, and feed off the developing grains, thus 

 spoiling them. Xumbers of larvse. are found in each ear, and 

 cause a disease generally spoken of as " red gum " or " red 

 maggot " by farmers. The larvae mature by the time the corn 

 is ripening, and many go down to the ground to pupate, the 

 puparia being orange-coloured bodies. Others which are not 

 full fed get harvested, and we find them often quite abundant 

 in the screenings. From these puparia next June the wheat 



