240 DIPTEEA OR TRUE FLIES. 



leave it and also pass to the next onion through the ground. 

 Pupation takes place in the ground, and in the decaying onions, 

 — the pupa is in a chestnut-brown puparium case, as in all the 

 Probosoidea. At the end of the year the larvae of the last 

 brood all pupate, and pass the winter as puparia in the ground, 

 some few being harvested with the onions. We frequently 

 turn up the chestnut-brown puparia in the winter, when digging 

 the beds over. The presence of onion fly can at once be told 

 by the leaves becoming flabby and turning yellow. When we 

 try to pull up the onion the leaves come off in the hands, the 

 plant being rotten. This rot is set up primarily by the onion 

 maggot, secondarily by fungi, bacteria, and damp attacking 

 the weakened bulb. 



Prevention and Remerlie/. — Applications of soot over the 

 young plants to ward off attack. Pulling up diseased plants 

 and destroying them with the enclosed larvse. Watering 

 around the young onions with paraffin emulsion. Early sowing 

 of seed, so as to get the plant well up before the fly comes. 

 Lightly earthing up the rows, so as to prevent the fly from 

 depositing her eggs : the larv» cannot crawl far when young, 

 and thus die from want of food. Sprinkle common washing- 

 soda along the sides of the young plants, or hoe in vaporite. 



Cabbage-root Flies (Phorbia brassio.e, See.) 



Cabbages and turnips are often attacked by the larvae of the 

 above, — small white grubs, cylindrical in form, tapering to a 

 point towards the head end like the onion maggot. These grubs 

 may produce swellings or galls on the roots of cabbage, and tunnel 

 in the lower parts of the stalk ; these galled parts decay in wet 

 weather, and not only stop the plants from growing but often kill 

 them outright. They go on appearing all the year, there being 

 a number of successive broods. When the larva is full grown 

 it leaves the plant and turns to a brown puparium in the earth, 

 speckled with dark-brown. We find maggots in the very early 



