230 VEGETABLE FOES AND DISEASES 



being pale grey, and the pincers white. The length 

 of the insect is about one quarter of an inch. In the 

 female, the forehead is broad, with a reddish-brown, 

 vertical medium stripe, and the body is more ochreous 

 in colour than the male. 



The Onion Fly causes serious injury to the Onion 

 crop in some seasons, large percentages of the plants 

 being quite spoiled, both in large and small areas. The 

 first indications of its presence are shown by the largest 

 leaves of the Onion plants becoming yellow and after- 

 wards whitish ; if these are pulled they come easily 

 away from the stem, and gradually the other leaves 

 become yellow and decay. The bulb will be found 

 to be small and badly shaped, and to have yellowish 

 maggots within its folds feeding upon it, this eventu- 

 ally causing it to become rotten and useless. In other 

 cases the outer or lower leaves of the plants are seen 

 to be lying on the ground, still green, whilst the leaves 

 remaining upright and green feel soft and flabby. If 

 infected plants are examined it will generally be noticed 

 that in the case of very young plants they are eaten 

 through just above the swelling bulbs by the maggots 

 or larvae of the fly. In older plants, with large bulbs, 

 maggots of all sizes will be found within the bulbs. 



The flies appear in early summer, and the female 

 lays six to eight eggs on an Onion plant upon the 

 leaves, and just above the ground or on it. The eggs 

 are white, long-oval and readily seen with a pocket lens. 

 Larvae, called maggots, come from the eggs in from 

 five to seven days, and make burrows down into the 



