206 THE NORTHERN MICROSCOPIST. 
wings and legs. Of its larval and pupal stages I can only say,— 
in the absence at present of exact information—that they must 
resemble very closely those of the English Gnat, the successive 
developments being probably more rapid owing to the favourable 
conditions of tropical light and heat. The Gnat completes its 
growth from the egg to the perfect insect in from three to four 
Fig. 39. 
weeks. As is the case with so many of the insect tribes it is 
aquatic in its larval and pupal stages, but draws its supply of air 
direct from the atmosphere. The eggs are laid on the surface of 
standing water in curious boat-shaped masses, which float about 
until the larvae emerge. ‘The larva possesses a round flattened 
head, furnished with two simple eyes, a pair of powerful mandibles 
clothed with cilia and two tufted antennz. ‘The thorax is usually 
described as proportionately much larger, although in a mounted 
specimen I have, it is decidedly smaller. The abdomen is long 
and slender, composed of ten segments, of which the last two bend 
away from the body at a sharp angle, while from the eighth a 
remarkable tubular column is extended, containing two tracheal 
tubes, which, dividing at the base of the column, pass up along the 
abdomen and thorax to the head, branching freely. It is by this 
column brought to the surface of the water that the larva breathes. 
The ninth and tenth segments also possess tracheal branches, the 
latter terminating in an exquisite arrangement of fringed hair-like 
bodies, in shape suggesting an opened fan, from which spring four 
taper conical organs, each traversed by an air tube. In from two 
to three weeks the larva becomes the pupa. The head disappears 
within the thorax, which is greatly enlarged, while the abdomen is 
relatively very slender and usually seen curved round under the 
thorax. The abdomen has now only eight segments, and the 
curious terminal appendages of the larva give place to two flattened 
plates at the extremity of the body. ‘The breathing apparatus is 
