FLIES AND THEIR WATER BABIES 69 



number of hooks on the lower end of its pupa 

 case, and waves its hairs about in the water 

 to draw a current of air within. 



Before very long the Sand-fly is ready to 

 leave its prison. But what is it to do ? How 

 can a little gauzy-winged fly escape through 

 the rushing water? Surely it will be swept 

 away and never reach the air and sunshine. 



Well, a short time before the fly is ready to 

 come forth the pupa case swells with air until 

 it is almost as round as a ball. Then the skin 

 splits and out comes a silvery bubble of air 

 that rises swiftly to the top of the water. 

 Directly it reaches the air the bubble bursts 

 vanishes like a fairy coach and the dainty 

 little fly which was within steps lightly on 

 the surface of the stream. 



Did ever fairy Prince ride in a more wonder- 

 ful coach than this little crystal globe, which 

 carries the fly in safety to the sunshine, up 

 through the rushing water ? 



