184 



THE STUDY OF FRESH-WATER ANIMALS. 



STUDY OF A LIFE-HISTORY. 



The Common Gnat 

 (Culex pipiens). 



We commence at the stage at which this insect is likely 

 to be observed first, viz. the larval stage. In early spring 

 when the aquarium jars are being stocked, these larvae 

 should be obtained. Most boys in the country know them 

 under the name of "wrigglers," because of their jerky 

 movements in the water. They double themselves into a 

 loop, suddenly straightening themselves again, and in this 



way they rise to the 

 surface. They may 

 be seen falling pas- 

 sively (Fig. 72). 



If the jar in which 

 these wrigglers are 

 pub is kept under 

 observation the 

 wrigglers will be 

 observed to be grow- 

 ing in size rapidly, 

 especially if food is 

 plentiful and the 

 room is not too cold. 

 In the vessel may be 

 noticed, after a time, 

 floating near the 

 top, whitish ghost- 

 like shadows of the 



gnats. These are their moulted skins (cuticles) which 

 they shed from time to time as they grow. The larva 

 when fully grown may be half an inch long. 



After some weeks the form changes to that of a little 

 but bulkily- shaped creature like a comma. This is the 

 pupa, which although it does not feed is active when 



Fig. 72. Larva, pupa, and egg raft of Common 

 Gnat (Culex pipiens). (The eggs are drawn 

 upon a larger scale.) 



