GENERAL LIFE HISTORY 35 



ing places of the house-fly are the mews and the farm- 

 yards where manure is allowed to accumulate ; the 

 house-fly has a preference for horse dung before cow 

 dung, which is preferred by some other kinds of flies ; 

 however, near towns, the domestic dust-bins, heaps of 

 market garbage, and deposits of town refuse give rise 

 to a worse plague of house-flies than stables. All these 

 flies deposit batches of white eggs, and are careful to 

 place them as much as possible in crevices and shielded 

 from exposure to strong light, or from draughts. 



The two house-flies and the blue-bottle have similar 

 larval stages, but their larvae, called maggots, differ. 

 The larvae avoid daylight and cannot withstand dryness. 

 As the larvae feed, they have the power of ejecting or 

 excreting a juice, which dissolves the food before they 

 imbibe the material ; their mouths are suctorial and 

 are destitute of teeth or biting jaws. 



The larva of the house-fly is an eyeless and legless 

 maggot, one half inch long when full grown and ex- 

 tended ; twelve cylindrical segments may be counted 

 in its body, or even thirteen if we separately distinguish 

 the small head segment, which may be withdrawn, and 

 but little observable ; five or six rear segments are of 

 nearly equal stoutness when only half grown ; after- 

 wards counting from the three stoutish rear seg- 

 ments, the others taper towards the very small head. 

 The middle and rear segments have pad-like bristly 

 processes underneath, which aid the maggots in 

 creeping, in which action they also make much use 

 of the head segment's grappling hook. The maggots 

 feed voraciously, but they seem, like the larvae of the 



