COMMON FLY-LAIRS %$ 



that they like to sleep and pass their lives. But should 

 the female find no stables or manure convenient when 

 she wishes to lay her eggs, she must search for and find 

 the next best place for her brood of young. Then she 

 will probably go to some human excrement in a back- 

 yard or garden privy, or, failing to find this, she will 

 go to a pigsty, or search out a fowl-house, or cowshed, 

 or farmyard. In towns she will find plenty of suitable 

 places the gutters, the mews, the abattoirs, the blind 

 alleys in the slums, the ash-bins, the dust-heaps, the 

 piles of forgotten banana-skins, the offal outside 

 bakeries and butchers' shops and stalls, the masses of 

 manure in gasworks, the horses' " bedding " in trades- 

 men's stables, the chicken-runs and pigeon-lofts, and 

 all accumulations of garbage found in many factories, 

 yards, streets, courts, and receptacles for kitchen slops. 

 These are the house-flies' breeding-places. 



The eggs are laid in batches, little clumps in and 

 around any putrid, fermenting, and rotting thing. 

 Each female fly lays on the average 120 eggs at a 

 sitting (Howard). Each egg is a small oval object 

 about one-twentieth of an inch in length. When first 

 laid it is white and may be distinguished easily with a 

 hand-lens, though it can be seen by the naked eye. 

 When we know the nature of the object searched for 

 it is usually soon discovered, and this applies to fly- 

 eggs in manure or refuse. A stick is useful in finding 

 them. 



The length of life in the egg stage varies with the 

 temperature of its surroundings. In hot summer 

 weather the eggs may hatch in eight hours from the 

 time they were laid ; but this period may be delayed, 

 according to Professor Newstead, for four days. On 

 a warm day, however, the egg hatches twelve hours 



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