THEIR RELATION TO MAN 



201 



cellar or store-room; a very little material serving to 

 mature a large number of specimens. The common 

 house fly, Musca domestica, prefers horse-manure for its 

 development and is most numerous in the vicinity of 

 stables. The eggs are laid in little masses by the adults, 



FIG. 92. Foot of the house fly: a, the last tarsal joint and claws; b, claws and 

 pulvilli; c, a small section of the pulvillus, showing hooked hairs. 



the larvae or maggots hatch almost at once, and a week 

 later these are full grown and ready to transform. 



On the soles of their feet flies have pads of very fine 

 hair, which serve excellently as gatherers of micro- 

 organisms from the surfaces over which they travel, and 

 equally well as distributors on others over which they 

 may track later. This point has been proved experi- 

 mentally by allowing flies to walk over cholera excre- 



