METAMORPHOSES OF THE GNAT. 



351 



is furnished with fin-like bunches of minute hairs, as likewise are the 

 segments of the abdomen. To the extremity of the tail is appended a 

 group of moveable leaflets or fins, so disposed that by their action they 

 sustain the larva at the top of the water, where it generally remains 



Fig. 177. 





Metamorphoses of the Gnat (Culex pipiens) : A, Boat of eggs. B, a, 6, c, some of the eggs 

 magnified ; d, another, showing the lid open for the escape of the larva. C, Larva. D, Pupa. 

 E, Larva magnified, showing e, the respiratory tube; /, the anal fins; gg, the antennae. 

 P, the perfect insect, magnified: a a, antennae; 6, rostrum. 



suspended with its head downwards. Such a position would obviously 

 render respiration impossible was there not a corresponding arrange- 

 ment of the breathing organs to allow of free communication with the 

 air. For this purpose, the respiratory tracheae are found to be con- 

 nected with a tube appended to the antepenultimate segment of the 

 abdomen, the perforated extremity of which, being raised above the 

 water, procures from the atmosphere the oxygen required for respira- 

 tion. After several moults, the larva, having attained its full growth, 

 enters the pupa state, and in this condition still remains an inhabitant 

 of the water, and occupies a position near the surface. A remarkable 

 change, however, is visible in all parts of its structure. The head and 

 thorax (fig. 177, D) are consolidated into one large mass, under which 

 the lineaments of the mature insect may be detected ; while the tail 

 still continues to be the agent employed in natation. The condition of 

 the respiratory organs, moreover, is completely altered : the tube fixed 

 upon the antepenultimate segment of the larta has totally disappeared, 

 and instead of it we find two tubes appended to the back of the thorax ; 

 these, although they perform the same office as the anal pipe of the 

 larva, arc thus displaced in order to correspond with the altered posi- 



