ROOT CROPS. 37 



• quarter of an inch long. The maggot turns to the pupal 

 stage in the ground. During the summer the pupae are 

 transformed into perfect insects in about twenty-five days. 

 The female flies finally give rise to eggs, maggots, and 

 pupse ; the latter hibernate in the ground until the follow- 

 ing spring. The yellow body of the fly is about a quarter 

 of an inch long, and carries two wings of a blackish-green 

 colour. 



Prevention. — (1) Good cultivation. (2) After thinning 

 top-dress the crops with soot and nitrate of soda. 



Fig. 14. — Caeeot Fly {Psila rosa). 



A. Carrot Ply (enlarpred). 



B. Legless larva (enlarged). 



C. Transverse section of a carrot, showing a "bnrrow " made by the lanrae of 



PsUa. 



Cure. — (1) Mix one pint of paraffin oil with two gallons 

 of water, and water the plants with the mixture after 

 thinning. - (2) Top-dress the crops with sand saturated 

 with paraffin oil. (3) " An injured crop should be lifted 

 early, the ground thoroughly limed and deeply ploughed. 

 This destroys the pupse, and prevents a renewal of the 

 attack in some future season." (4) Farmyard manure, 

 mixed with salt and ploughed into the land during the 

 autumn, destroys the pupse. 



