DAHLGREN, THE MALARIA MOSQUITO 



17 



Anopheles larvae exhibit a curious habit of suddenly twisting the head. 

 The peculiar, almost audible "sua])" or "click" with which the sudden 

 turning is accomplished is very characteristic. On this account the 

 name "head-turners" has been proposed for them. 1 



The larva feeds with its head turned so that the lower side, which 



bears the mouth, is directed upward. The moustache-like brushes, by 



rapidly sweeping the under side of the surface-film of the 



... „ . . . . Manner of 



water, set up a current which carries food into the mouth. feeding 



Small particles which become entangled in the brushes are 

 combed out by stout curved hairs, three or four of which are borne on 

 each mandible, the brushes bending back into the mouth for this purpose 

 from time to time. 



The food of the larva consists 

 of the microscopic animals and 

 plants which abound at the sur- 

 face of the water. Little dis- 

 crimination seems to be exercised 

 in the choice of food, anything 

 which is carried into the mouth, 



RESPIRATORY FUN 

 OF PUPA"" 



Food of 

 Larva 



even sand "rains, beino' 



PATAGIUM 



FIG. 12. MATURE LARVA OF ANOPHELES. 



Ventral surface. The figure .shows 

 clearly the formation of the thorax of the 

 future insect within the larval thorax. 

 Magnification, l'A diameters. 



sometimes voraciously 



swallowed. The in- 

 testine, which is practically a 

 straight tube, may usually be 

 seen in the rather transparent 

 living animal, colored dark by its 

 contents. The entire larva often 

 appears green from ingested 

 algae. 



The Malaria Mosquito larva may be readily distinguished from the 

 larva of the Culex Mosquito by the shortness of its siphon and its hori- 

 zontal position in the water. The common "wrigglers" have elongated 

 siphons and are always found hanging obliquely, or even vertically, head 

 downward, the tip of the siphon only reaching the surface (Fig. 10). 



The larvae of certain mosquitoes are known to hiber- 

 nate, and may remain throughout the winter frozen in the 

 ice, coming to life when the ice melts in the spring. Professor Smith 



'Minot.C. 8. Notes on Anopheles. Boston Soc. Med. Sei. 1901. 



Hibernation 



