30 THE FLY-EGG, LARVA, AND CHRYSALIS 



thrust out ; and slowly the flying insect is born like 

 the delivery of an aeroplane from its hangar to live its 

 life of freedom. The full-grown fly leaves its old home 

 the pupa-case with its mummy-clothes to take care 

 of itself, and it pushes, walks, or crawls away from its 

 former surroundings. If it encounters obstacles it 

 pushes its way through them by simply inflating the 

 bag in front of its head ; or by alternately inflating 

 and deflating the sac, it bores its way through the soft 

 manure bed. But usually the larva is wise enough to 

 enter the chrysalis stage at the edge of the manure-heap, 

 for it foresees possible difficulties of this nature, and 

 then the use of the bag after birth is not required. But 

 nevertheless this bag is being constantly tried in case 

 of eventualities. Arrived at the edge of the wood, the 

 home where the early life was passed, the fly tries its 

 wings. These have been closed over the back of the 

 body but kept separated from each other. Now they 

 are opened and shut and soon grow harder and stronger. 

 The insect then cleans its legs by rubbing them together 

 or by stroking the forelegs with the hind ones ; and at 

 last opening its wings wide, the house-fly sails away on 

 the wind in search of food and adventure. 



From the foregoing, it will be realised that the best 

 time to undertake fly-reduction is during these stages 

 of fly-life which are known as the larval metamorphosis. 

 The flies are then congregated in clumps and clusters, 1 

 they are crawling maggots living together in hundreds 

 and perhaps thousands within a small area, and these 

 maggots or grubs can be seen easily, cannot escape, and 

 may be destroyed in large numbers. On the other 



1 It has been estimated that one female fly can produce in one month 

 506,250,000 offspring. Supposing only half of these survive the larval stages, 

 we have the enormous total of 250,000,000 increase per month. 



