222 DIPTERA OK TRUE FLIES. 



the thorax is yellow, and has three dark blackish-green stripes 

 on it ; the abdomen is greenish-brown with dark bands across. 

 The female lays her eggs separately, one larva sufficing to pro- 

 duce this gouty ajipearance. She deposits them on the barley 

 plant just when the ear is still in the sheathing leaves, either 

 within the leaves or so that the young larv» can .speedily enter. 

 The larvEe first devour some of the developing grain on one side, 

 and then commence to tunnel down the stem to the first node, 

 forming a small Ijlack passage in which the grub turns to a 

 yellowish -brown puparium. From this there aj^pears a second 

 brood of flie.s, which deposit their ova on various wild grasses, and 

 pass the winter in them. That is the reason why we always 

 find this gout attack most marked round the borders of the 

 fields and along the grassy headlands, and any rough grassy 

 ditch running across the land. Sometimes the plant is suffi- 

 ciently strong to come out of its slieathing leaves, and then we 

 can detect its presence by some of the grains having gone, and 

 by the black tunnel extending from the ear down to the first 

 node. 



An Ichneumon ( Ccditiius nir/er) attacks the Gout Fly larva 

 (fig. 11 2, 4 and 4a), also a small Pteromalus described by Curtis 

 as P. micans. 



Prevention and Remedies. — Early sowing is one of the best 

 preventives, and the application of stimulating dressings to the 

 crop so as to carry it along. Mowing down the rough grasses 

 round the headlands, &c., in the winter and burning them will 

 kill numbers, for they are found breeding in such places in the 

 winter and also hibernating as adults there. 



The Frit Fly (Oscinis frit). 



Oats are often seriously injured past recoverj' by a small 

 larva in the centre of the plant. This is the larva of a small 

 black fly, the Frit Fly, which belongs to the family Oseinidm. 

 We notice this pest by the young crop withering away in 



