THE COMMON MOSQUITO 



71 



is not known, but which may possibly function as gills 

 while the larvae are very young-, and are certainly of use as 

 swimming organs. When 

 the breathing tube is at the 

 surface of the water the 

 body of the wriggler ex- 

 tends down below the sur- 

 face at more or less of an 

 angle with the water sur- 

 face, and its mouth-parts, 

 as just stated, are constant- 

 ly in vibration, bringing 

 into its mouth any minute 

 particles which float in sus- 

 pension in the water. Oc- 

 casionally it descends to 

 the bottom, jerking its body 

 violently from one side to 

 the other. The flaps at the 

 end of the body undoubt- 

 edly assist in this motion. 

 The jerking motions are 

 not so evident when 

 larva or wriggler is 

 scending" as when it 



the 

 de- 

 be- 

 comes necessary for it to 

 ascend once more ; in other 

 words, its specific gravity 

 seems to be greater than that of the water and sometimes 

 it can be seen to descend without effort, simply sinking 



Fig. 9. — Full-grown Larva of Culex 

 punge?is ; enlarged. (Author's il- 

 lustration.) 



