86 



In Dixa there is no globular thorax, and the 

 whole larva is longer and thinner than an 

 Anopheline larva (8 mm.) Moreover, Dixa larva 

 only indents the surface film at the head and tail, 

 there being no palmate hairs on any of the 

 segments. Dixa larvae move very rapidly, and 

 have a habit of climbing above the surface of the 

 water and resting in a loop with the head and tail 

 downwards. When placed in a specimen tube it 

 climbs up the side and becomes lodged in crevices 

 in the cork. 



It is found frequently in running water 

 (Fig. 20). 



Mochlonyx Larva. — Note absence of palmate 

 hairs on dorsum and presence of respiratory syphon, 

 but less developed than in a Culicine. They are 

 extremely voracious. They lie deep in the water. 



Corethra Larva. — These are the so-called 

 ' phantom ' larvae. They are extremely trans- 

 parent, and lie horizontally rather deep in the 

 water. The head is smaller than in Anophelines. 

 There is no syphon communicating with the 

 external air. They are extremely voracious. Add 

 some Corethra larvae to a tumbler containing Culex 

 larvae. 



Stegomyia. — The larva of Stegomyia is rather 

 longer than that of Culex. When disturbed it ex- 

 hibits a rather lashing movement like that of cer- 

 tain small aquatic worms. When at rest at the 

 surface, the attitude of the body is almost vertical 

 The larva, however, spends a good deal of its time 

 browsing at the bottom of the water, and then 

 lies for the most part horizontally. 



The head is small in proportion to the rest 

 of the body, and the thorax is less conspicuously 

 marked off from the abdomen than in Culex. 



