PREVENTION. 



53 



These are jjoints of general application^ — a sort of 

 physical-force treatment. Bury the enemy beforehand 

 if you can ; but if you have it in the ground where it 

 can do harm, then (as far as you can), keep your crop 

 grubs, and your coming crops, at a distance ; and in 

 cases where the Flies require to lay their eggs on a 

 bulb, or to go down cracks to get at the roots, then 

 ■think over the matter well as to whether some such 



Fig. 46. — Cabbage and Potato Flies : 1-3, maggot arnl pupa-case of 

 Cabbaue Fly ; -1 and 5, Root-eating Fly ; 6-9, Potato Fly and maggot : 

 all magnified, with nat. size. 



way as I have suggested (or some much better way, 

 which you may think of for yourselves) cannot be 

 managed so as to defend the plant, — to lock the door, 

 as it were, in face of the thief. The Fly has got to 

 lay her eggs, and then she will die ; and if we can 

 protect our plants so that (as I have seen with Onion 

 Fly) the eggs have to be dropped at haphazard, where 

 they would come to nothing, it saves much future 

 trouble. 



But besides methods of prevention based on pro- 

 tecting the plant from egg-laying, or on burying down 

 the infestation, or carrying it away and destroying it, 

 something may be done by noticing, with regard to 

 some of the common crop fly maggots, that they not 



