140 Flies [ CH. 
of a skim coulter buries the pupae, and so prevents 
them giving rise to flies in the following spring. 
The screenings of infected wheat often contain flax 
seeds which should be destroyed. 
The grain of an infected crop should be carefully 
examined if used for seed. Couch and timothy should 
be kept down as much as possible. 
Wheat Bulb Fly (Hylemyia coarctata). 
This fly has been the cause of considerable loss to 
wheat growers. It is said to be bad after a bare fallow 
or a crop which only partially covers the land, but this 
has not yet been proved. 
The life history is not known with certainty, but 
seems to be very similar to that of the frit fly. The 
maggot is larger than that of the frit fly and reaches 
nearly 4 of an inch in length. It may be found 
during April feeding on the young shoot and thus 
stunting the growth and preventing the formation of 
ears. 
No satisfactory preventive measures have been 
discovered. 
Cabbage Root Flies. 
There are several flies whose maggots attack the 
roots of cabbage and allied plants, but a description 
of the cabbage root fly (Phorbia brassicae), which is the 
commonest, will serve to show the method of attack 
and how to deal with it. This fly attacks all cruciferous 
crops, but the greatest damage is done to cabbages, 
cauliflowers and turnips. 
When a cabbage plant is attacked the outer leaves 
turn yellow, the plant makes little growth and soon 
