MOSQUITOES. 



243 



posterior extremity which is called a respiratory syphon. This pro- 

 jects off at an angle from the axis of the body, the true end of which 

 terminates in four flap-like paddles. If you divide the length of the 

 syphon by the breadth, you get what is known as the syphon index. 

 In Culex the syphon is long and slender; in Stegomyia it is short and 

 barrel-shaped. When at the surface the Culex larva has his syphon 

 almost vertical and the body at an angle of about 45. 



A-H.Ebfclinpf ?-> 



FIG. 76. Metamorphosis of mosquitoes, i, 2, 3, 4 and 5, Eggs, larva, pupa 

 and heads of male and female Culex; 6, 7, 8, 9 and 10, eggs, larva, pupa and heads 

 of male and female Anopheles; n, 12, 13 14 and 15. Eggs, larva, pupa and heads 

 of male and female Stegomyia. 



The Stegomyia larva hangs more vertically. As a rule, the hairs 

 proceeding from the sides of Culex larvae are straight and the head 

 relatively large. There are also no palmate hairs along the sides. 



The Anophelinae larvae have a small head which is capable of 

 being twisted around with lightning-like rapidity. They are darker in 

 color and have no syphon; float parallel to the surface of the water; 



