220 DIPTERA OR TRUE FLIES. 



deposit their oval white eggs on the un Jer-surface of the mangold 

 leaves : these ova are usually placed in groups of two, three, or 

 four, close together, each egg being sculptured hexagonally. In 

 a week or ten days these ova hatch into small white maggots, 

 which burrow into the soft mesophyll layers of the leaf : there 

 these footless grubs live for four weeks, forming first a small pale- 

 green patch, which gradually grows into a white and then brown 

 blister. When held up to the light the maggots can be seen 

 within. On reaching maturity they mostly fall out to the 

 ground, where, as in all this group of flies, the skin of the larva 

 hardens and forms a brown jsuparium, as soon as the larva has 

 pushed its way an inch or two under the soil. In the summer 

 the fly comes forth in about two weeks. There are many genera- 

 tions in the year : the last all turn to puparia, and remain as 

 such in the soil and in the decaying leaves all the winter. The 

 sow-thistle also harbours this pest. The attack is sometimes 

 very serious, especially when the ova are laid on very young 

 plants. Sugar Beet is also attacked. 



Premntion and Remedies. — There are three points worth 

 mentioning : first, the destruction of winter puparia by the usual 

 methods of deep ploughing ; secondly, the application of some 

 stimulating manures to the attacked crop, especially nitrate of 

 soda ; and thirdly, spraying, where a " strawsoniser " can be 

 used, with paraflin emulsion. There being many generations, we 

 should try and kill the first. 



The Gout Fly (Chlorops TyENiopus). 



In poor land barlej' may often be seen stunted and swollen, 

 and unable to burst its way out of the ear. This peculiar 

 appearance is called " Gout," and frequently causes a serious 

 deficit in the crop. This swollen diseased state of the plant is 

 produced by a small fly belonging to the Chloropidce, called the 

 Eibbon-footed Corn Fly or Gout Fly (OMorops twniopus). It is 

 a small fly about one-eighth of an inch long, thickly built; 



