THE MALARIAL MOSQUITOES 



105 



great that it was not satisfied with the floating parti- 

 cles, and when it descended to the bottom it mouthed the 

 particles of sand, apparently swallowing the slime on the 

 little stones and frequently even picking up quite a large 

 sand pebble and then dropping it again. In this stage 

 the individual which grew most rapidly remained only 

 four days, and transformed to pupa on the morning of the 



Fig. 23. —Enlarged Head of Larva oi Anopheles macvHpennis, from side; 

 greatly enlarged. (After Nuttall.) 



17th, after a larval existence of sixteen daj^s. The accom- 

 XDanying figures of the larvae have been drawn Avith such 

 care that detailed description will be unnecessar}^ They 

 were drawn from life under the compound microscope. 

 Some of the structures are puzzling, notably the organs 

 occurring on the dorsum of the abdominal segments, 

 shown most plainly in Fig. 20, and which look as though 

 they might be spiracles until they are examined under a 



