THE MALARIAL MOSQUITOES 



101 



Fig. 19.— Half-grown Larva 

 of Anopheles maculipennis 



miniature maelstrom and enter the alimentary canal. The 

 spores of algc^, bits of dust, minute sticks, bits of cast lar- 

 val skins, everything- 

 ;^— in fact which floats, 

 follow this course, and, 

 <^/?'iP\K> watching- the larva un- 



der the microscope, 

 they can plainly be seen to pass 

 through the head into the thorax 

 until they are obscured by the 

 dark color of the insect's back. 

 enlarged. (Author's illus- Occasionally, too large a frag-- 

 tration.) ment to be swallowed with ease 



clog-s the mouth. Sometimes it enters the mouth and 

 sticks. In such cases the head of the larva revolves 

 with lightning-like rapidity and the fragment is nearly 

 always disgorged, / 



although some- 

 times it is swal- 

 lowed with an evi- 

 dent effort. Since 

 the Anopheles lar- 

 va feeds only upon 

 these light, floating 

 particles, its spe- 

 cific gravit}^ is near- 

 ly that of the water 

 itself, and it supports this horizontal position just beneath 

 the surface film with comparative ease, and, in fact, with- 

 out effort, the tension of the surface film itself being hardly 



Fig. 19a. — Same stage of 

 Culex ; enlarged. (Au- 

 thor's illustration.) 



