138 



General Biology 



man, though some members of the genus Culex do transmit it to birds. 

 (At least this is true in India.) 



The distinguishing characteristics of the two groups is as follows 

 (Fig. 51) : In Culex the wings are clear, while in Anopheles they have 



Fig. 51. 



A. — Life history of house mosquito (Culex). 



B. — Life history of malaria mosquito (Ano- 

 pheles). (From Howard, U. S. Dept. of Agri- 

 culture.) 



C. — Culex larva, showing details of external 

 structure. (After Riley and Johannsen.) 



brown spots. In Culex the axis of the body forms a curved line as 

 though the insect were hump-backed, while Anopheles presents a 

 straight line when resting. For those familiar with insect anatomy we 

 may add that Culex has short maxillary palpi while Anopheles has them 

 almost as long as its proboscis ; and lastly, for those with a musical ear, 

 we may add that the female Anopheles, which is the only one which 

 carries the malarial parasite, sings several tones lower than the Culex. 



The eggs of Culex are always laid in a mass, while those of 

 Anopheles are laid singly. As the eggs hatch, the larvae of Culex hang 

 from the surface of the water at about an angle of 45 degrees, while the 

 larvae of Anopheles lie almost parallel to the surface of the water. 



Prevention is always the scientific method of overcoming disease. 

 Because mosquitoes lay their eggs in quiet pools, men conceived the 

 idea of preventing these eggs from hatching. Such prevention of hatch- 

 ing has not been possible, but oil poured on the water kills the little 

 wrigglers after they have hatched. 



The breathing tubes of wrigglers are provided at their openings 

 with hydrofuge plates which will not permit water to enter. Since these 

 hydrofuge surfaces are due to the presence of oil, it is obvious that oil 

 poured on the surface of the water will mix with this and cause the 

 entry of oil into the breathing tubes, thus asphyxiating the wrigglers. 

 It has been thought that certain kinds of fish destroy eggs and wrigglers. 



