354 



THE WORLD OF ANIMAL LIFE 



although it hves in the water, does not breathe water, as the fishes 

 do, but respires air, just hke almost all other insects. When it 

 wants to breathe it rises to the top of the water, and there floats, 

 head downwards, with its little feathery tuft just poked above the 

 surface. 



Gnat grubs feed upon all sorts of fragments of animal and 

 vegetable substance. 



After a week or two, when they have changed their skins several 

 times, as all grubs do, and grown to some little size, they become 



chrysalids or pupae. Their shape 

 is greatly altered now, for the front 

 part of their bodies is swollen into 

 a large mass, in which the future 

 legs and wings are slowly develop- 

 ing. The tufted breathing-tube at 

 the end of their tails is gone, too, 

 and now they breathe through two 

 short tubes that project from the 

 upper part of the body. They 

 spend a good deal of their time 

 floating quietly at the surface of the 

 water, but they can s\\'im about, when they please, almost as easily 

 as before. But during this period they take no food, for their 

 mouths are covered over with skin. 



For a few days the gnat pupa; rest quietly at the surface of the 

 water, or swim gently to and fro. Then the last change takes 

 place. The skin of the pupa splits along the back and opens, 

 the perfect gnat creeps out, and, standing upon its own cast- 

 off covering, which serves as a kind of raft, proceeds to dry its 

 wings. And before long the insect is able to spread them and 

 fly away. 



When we examine the beak of a gnat through a microscope, 

 we find that that delicate little instrument is made up of no 

 fewer than seven different parts! First there is a kind of sheath 

 {t), in which all the other parts are packed away when they are not 

 in use; then there are five very sharp lancets (dfg), which are 

 employed in piercing the skin; and lastly, there is the tongue [e), 



Gnat : Organs of the Mouth 



