SI 2 DIPTERA. 
other ; but, in ascending through the 
water, the globule is constantly retained 
between the filaments, till they may be 
expanded on the surface. 
Lucy, What a quantity of air this 
little creature must have in its body! 
Mother. Naturalists have not yet as- 
certained how it is able to produce all 
this air, by the management of which it 
can sink or swim at pleasure. 
Lucy, What does the larva eat? 
Mother, It appears to live entirely by 
suction, as it has neither jaws nor tongue ; 
but in the middle of its mouth there is a 
single horny beak, like the upper part of 
a bird's bill, to each side of which is at- 
tached a short, fleshy organ ; and these it 
has the power of protruding, or of re- 
tracting, when not wanted. They seem 
to answer the joint purpose of hands and 
feet ; for, in the water, they serve to stir 
up the mud, so as to allow the beak to 
work in it more easily ; and they are em- 
ployed as feet, when the animal quits the 
water. 
