158 INJURIOUS INSECTS AND FUNGI. [Sept. 1896. 



by the attacks of this fly, while in cottage gardens and 

 allotments the whole of the plants on the small onion beds of the 

 cultivators are often ruined by successive generations of the 

 same insect. 



The first indications of the infestation are shown by the longest,, 

 or first 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, with 

 yellowish maggots within its folds, which feed upon it, and 

 eventually cause 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, while the leaves 

 remaining upright and green feel soft and flabby. 



If infested plants are examined it will be generally noticed that 

 in the case of very young plants they aie nearly eaten through, 

 just above the swelling bulbs, by the maggots, or larvse, of the 

 fly. In older plants with large bulbs, maggots of all ages and 

 sizes will be found within the bulbs. 



Onion plants that become yellow and show signs of drooping 

 should be examined for maggots just below the surface of the 

 ground. 



Life History. 



The male and female flies of this species differ slightly. The 

 male is dark grey in colour, with black bristles. The eyes are 

 red and close together. Upon the thorax are four bright brown 

 stripes and four rows of black bristles. The abdomen is ash- 

 coloured, rather narrow, having triangular black spots down it 

 which almost join each other. The legs are pitchy. 



In colour the female fly closely resembles the male, but the 

 abdomen is dark grey, with the end more pointed than in the 

 male ; and the eyes are wide apart. 



From six to eight eggs are laid on an onion plant, upon the 

 leaves and just above the ground. The eggs, which are white, long, 

 and somewhat oval, can be easily seen without a glass. Maggots 

 (larva?) come from the eggs in from five to seven days, according* 

 to the temperature and other conditions, and make burrows down 

 into the root, or bulb, between the shtathing leaves. They feed 

 upon the contents of the cylindrical root which can hardly at 

 this stage be styled a bulb, and move on to other plants 

 Later on, when the bulbs are larger, they are occupied by many 

 maggots, which feed on them and cause them to become rotten. 

 Sometimes the bulbs will be seen to be swarming with maggots, 

 and the earth round them is also infested. The maggot 

 continues in the larval state for a period varying from 13 to 15 

 days, feeding throughout this period upon the onion roots, 

 or bulbs. It is nearly four lines (one-third of an inch) in 

 length, dull yellowish white, or dirty white, in colour. The head 



