THE RAT- TAILED FLY, Oli DRONE FLY. 267 



respires atmospheric air, but does so in a different 

 manner. Instead of obtaining air through the tail, it 

 breathes through some little tubes which are placed 

 in the thorax. The body is much curved, and the 

 creature, although it can move about, has not its 

 former activity, and is unable to eat. 



The large size of the pupal skin is the last feature 

 in the water trespassing habits of the Gnat, as with- 

 out it the perfect insect would never be able to free 

 itself from the water. As it is, when the Gnat is fully 

 developed it rises to the surface, and then, with a 

 powerful movement, splits the skin throughout a con- 

 siderable portion of its extent. The split skin opens 

 out, and forms a sort of boat, which is very buoyant. 

 The Gnat slowly draws itself out of the skin, and, 

 standing upon its cast garment, moves its wings in 

 the air until they are dry and firm, and then takes 

 flight. 



THE RAT-TAILED FLY, OR DRONE FLY (Eristdlis 



Here we have another of the numberless examples 

 in which a slight and simple modification of form 

 enables a creature which breathes atmospheric air to 

 exist while under water. 



We are all familiar with the common Drone fly, 

 which is so plentiful in the summer time, and which 

 looks so very much like a bee. In its perfect state it 

 is a denizen of air, darting along with such velocity 

 that the eye can scarcely follow it. But in its pre- 

 liminary stages it is a dweller in the water, or rather 



