DIPTEKA OR TRUE FLIES. 217 



vested with the onions. "We frequently turn up the chestnut- 

 brown pupaxia in the winter, when digging the beds over. 

 The presence of onion fly can at once be told by the leaves 

 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 a fungus and 

 damp attacking the weakened bulb. 



Prevention and Remedies. — Winter destruction of the puparia 

 by the use of gas-lime. Applications of soot over the young 

 plants to ward off attack. Pulling up diseased plants and 

 destroying them with the enclosed larvae. 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 larvae cannot crawl far when young, and thus die 

 from want of food. 



Cabbage-root Flies (Anthomyia BRASsiciE, &c.) 



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 

 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 gaU and turns to a brown puparium in the earth, 

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

 spring as well as puparia. The Cabbage Fly {A. brassieai) is 

 ashy-grey, and hatches from the puparium in about three weeks : 

 the male has a black stripe down the abdomen and three on the 

 thorax. The galls on turnips must not be confused with those 

 of the Turnip -GaU Weevil (Centorhynchus stdcicollis). The 

 Kadish Fly (A. fioralis) has a spiny maggot ; A. radicum (fig. 



