ROOT CROPS. 



37 



qiiarter of an inch long. The maggot turns to the pupal 

 stage in the ground. During the summer the pupse 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. 



c n 



Fig. 14. — Cabhot Fly (Psila rosce). 



A. Carrot Fly (enlarKed). 



B. Legless larva (enlarged). 



C. Transverse section of a carrot, showing a " burrow " made by the larvse of 



Psila. 



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. 



