Sept. 1896.] 



INJURIOUS INSECTS AND FUNGI. 



159 



part of its body is sharply pointed, and the head, furnished with 

 a pair of black hooks, can be extended at will ; the tail end is 

 cut off obliquely flat, and in the centre there are two brown 

 spiracles or breathing tubes, while the margin of the flat tail 

 end there are eight teeth, or projections. 



Before pupation takes place, the maggot usually goes into the 

 earth. Sometimes pupation occurs within the onions. The 

 pupa, or rather the pupa case or puparium, is chestnut brown, 

 oval, not so long as the maggot, and has the same toothlike 

 projections on the caudal end. On opening this puparium the 

 white pupa will be seen with the embryonic wings of the future 

 fly, which appears in from 13 to 16 days after pupation. 



There are several generations of this insect. The first has 

 been seen as early as the 25th of April in very forward seasons, 

 and flies have been noticed through the autumn, and as late as 

 November. Curtis states, moreover, that he saw them alive in 

 December. 



Methods of Prevention and Remedies. 



Spraying onion plants with offensive compositions is a good 

 way of preventing infestation. Paraffin emulsion is as good a 

 compound as any for this purpose. It may be made by 

 thoroughly mixing together 3 pints of paraffin and \ lb. of 

 soft soap with one gallon of boiling water. Mixing may be done 

 by passing the composition through a hand pump, once or twice; 

 6 gallons of water should be added to dilute it sufficiently, so 

 as not to burn the onion leaves. When the onion leaves are 

 young and very tender 7 or 8 gallons should be added. It may 

 be applied on small plots of onions with a Knapsack machine ; 

 on large breadths with a horse distributing machine. The 

 spray should be dense and in the form of mist. This operation 

 should be performed early in the season, when the onions have 

 established their leaves. 



Spraying must be repeated, probably twice or thrice, especially 

 if heavy showers fall after the process. 



When onion plants in a field or garden are noticed to droop 

 and wither, all such plants should be taken up and burnt, or 

 deeply buried. They must be taken up by means of a little three 

 pronged fork, or some other handy tool, so that every particle of 

 bulb and leaf is removed. 



Wherever it is possible, onions should not be grown again, for 

 at least one season, on land where this crop has been infested, as 

 the pupae remain in the ground during the winter. All pieces 

 of bulbs should be got off infested land, as pupae occasionally 

 remain in the bulbs. If it is necessary to take two successive 

 crops of onions on infested land the ground should be dug very 

 deeply, two spits deep, and well limed or gas-limed. 



Sprinkling the young onions with soot has been adopted with 

 some advantage, but the pungent odour soon evaporates and it 

 is necessary to give several dressings. 



