THE MALARIA PARASITE 519 



The diagram 1 (Fig. 61) represents in graphic form the asexual 

 and sexual cycles of reproduction of the malaria parasite. 

 So far as is known, malarial infection is conveyed only 

 through the bite of infected mosquitoes of the sub-family 

 Anophelince. It has been repeatedly proved that infected 

 mosquitoes convey infection, and that if mosquitoes be 

 excluded human beings may live in the most malarious 

 districts without contracting the disease. 



Mosquitoes (Culicidce) are distinguished from other mosquito- 

 like insects by the fringe of scales on the wings. The common 

 mosquitoes belong to the sub-family Culicince. The Anophelince, 

 are usually less abundant (but there is great variation in different 

 districts), and bite mainly at night ; the females alone are blood- 

 suckers. Some species breed in natural collections of stagnant, 

 others in slowly running fresh, water well supplied with lowly forms 

 of vegetable life. If the head of a mosquito be examined with a 

 hand-lens, three sets of appendages will be noticed. In the middle 

 is the stout proboscis containing the stinging and suctorial appa- 

 ratus ; situated at the base of this are two palpi, one on either side, 

 and outside these again are two antennae, which are more or less 

 hairy. In Anophelince, both male and female, the palpi are as long 

 as the proboscis ; in the female Culex (also in Stegomyia and many 

 other genera) they are short and stumpy. In Anophelince the scales 

 on the veins of the wings are usually arranged in alternating light 

 and dark patches, giving a speckled or dappled appearance, different 

 as a rule from anything seen in Culex. (Some Culices have a similar 

 arrangement, and it is wanting in A. maculipennis and A. bifurcatus.) 

 The front or costal margin of the wing in Anophelince is almost 

 always marked with dark blotches. Anopheles, as a whole, is a 

 more slender insect than Culex, and when at rest its body is all in 

 one line, whereas Culex is angular or hump-backed. The important 

 species known to carry malaria are Anopheles maculipennis in Europe, 

 N. Africa, and N. America, A. bifurcatus in Europe, Myzomyia 

 funesta and Pyretophorus costalis in Central and W. Africa, and 

 Cellia argyrotarsis in tropical America. Other species, e.g. Myzo- 

 rhynchus sinensis, Cellia Kochii, and others, are less important 

 carriers. 



(On Mosquitoes, see Theobald, Brit. Museum Monograph, and 

 Allbutt's System of Med., ed. 2, vol. ii, pt. 2 ; Giles, Handbook of 



1 This figure is reproduced by permission from Daniels' Laboratory 

 Studies in Tropical Medicine (Bale, Sons, & Danielsson, 1908). 



