ONION FLY 231 



root or bulb between the sheathing leaves. They feed 

 upon the contents of the stem or where a bulb would 

 form, and move on to other plants. Where the bulbs 

 are larger they are occupied by many maggots, feeding 

 on and causing them to become rotten, and in some 

 cases the earth round the bulbs is also infested. The 

 maggot continues in the larval state about a fortnight. 

 When full grown it is about one third of an inch long, 

 dull yellowish-white or dirty-white in colour. The 

 head part of the body is sharply pointed, and the head 

 furnished with a pair of black hooks, which can be ex- 

 tended at will. The tail end is cut off obliquely flat, 

 and in the centre there are two brown breathing 

 tubes, and on the margin of the flat tail end there are 

 eight projections. Before reaching the pupa stage the 

 maggot usually goes into the earth, but sometimes 

 remains within the Onion. The pupa, or its case, is 

 chestnut-brown, long-oval, and from the pupa case the 

 fly appears in from thirteen to sixteen days. In a 

 season there are several generations of the fly. The 

 first has been seen as early as the 25th of April, and 

 flies have been noticed as late as November. 



Prevention. i. Spraying with offensive composi- 

 tions, (a) Paraffin emulsion made by mixing three 

 pints of paraffin oil and half a pound of soft soap with 

 one gallon of boiling water, mixing being thoroughly 

 done by churning with a hand pump, adding seven 

 gallons of hot water when the Onions are young, and 

 six gallons when they are forming bulbs. The spraying 

 should be dense and in the form of a mist, operating 



