Larvae and Pupae 65 



insects and fish, and with no hiding places for the 

 larvae, are almost sure to be entirely mosquito free. 

 Shallow, stagnant water, especially if in a deep 

 hollow, or among bushes or trees, is an ideal breed- 

 ing place. The pools covered with " green scum," 

 at which the unsophisticated point with a shudder 

 as " dreadful malaria holes," as a matter of fact, are 

 generally nothing of the sort. "Green scum," if 

 Spirogyra, entangles the wigglers and drowns 

 them ; duck weed often covers the surface so 

 densely as to choke them ; and Englena, a favourite 

 protozoan food, may grow, at least in very small 

 pools, so thick at certain times of the year as to 

 swarm at the surface in such numbers that it forms 

 an impenetrable film. In such pools, too, many of 

 the aquatic insects love to hide, and soon reduce the 

 surplus mosquito population. 



Cisterns and old wells are often breeding places, 

 also the bases of flower-pots, vases where flowers 

 have stood for several days, potholes in the rocks, 

 tin cans, or almost any other receptacle that will hold 

 water. Some species, as tcrritans, will breed almost 

 anywhere ; others, as A. barbcri, must have a certain 

 sort of locality, in this case a hollow tree. Anopheles 

 will breed in clear water or in sewage ditches. 



Internal Anatomy. — In the brief general descrip- 

 tion of the larvae, given on previous pages, no mention 

 was made of the internal anatomy, and but brief 

 notice was given to the mouth-parts. 



The musculature of the larvae is too complicated 

 to be here described, as is also the minute anatomy; 

 but after one has studied the intricate muscle system 



5 



