138 MOSQUITOES AND MALARIA [CH. 



Other species are pool-breeders, and some may even restrict 

 themselves, or be able to flourish only in some particular kind 

 of pool. Thus the numerical prevalence of the common Indian 

 species /I. (Myzoniyia) rossii is dependent usually on the occur- 

 rence of small freshly-filled shallow muddy ram-pools, such as are 

 formed in countless thousands during the Indian monsoon. In 

 the forests of South America a malaria-transmitting species, A. 

 [Myzomyia) lutzi, breeds in various pitcher-plants, and especially 

 in the cups of various epiphytic tree pines. An even more 

 remarkable choice of breeding place is seen in the Malayan 

 species A. (Lophoscelomyia) asiatica, which is found breeding 

 only in bamboos that have been perforated by a borer. 



Over a large tract of the earth's surface, where mangrove 

 swamps and salt marshes are a feature of the sea coasts, the 

 species A. {Myzomyia) ludlowi breeds in brackish water, in pools 

 that are entered by the sea at spring tides. In the case of the 

 Andaman Islands, Christophers has recently shewn that this 

 species is the chief carrier of malaria, and as it is not found at a 

 greater distance than half-a-mile from the coast, is the cause 

 of a littoral distribution of malaria in these islands. 



Another good example of the extent to which habits of 

 particular species in regard to the choice of breeding place may 

 affect the dissemination of malaria is seen in the case of the 

 very interesting /I «o/)/jt'/es, A. (Nyssorhynchus) stephensi. This 

 species ordinarily is found in pools in large sandy river beds, 

 and has a predilection for quite small collections of water, 

 such as the hoof-marks made by cattle coming to drink, or 

 shallow surface wells made in the sand at the river margin. 

 It was found, however, by the Royal Societies Commission, 

 to possess, like Cuhcines, the power of breeding in water pots 

 and other domestic utensils, when these were filled with com- 

 paratively clean water. More recently this species has been 

 shewn by Listen and by Bentley to be the species concerned 

 in the spread of malaria in Bombay City, where the population 

 is as dense as in the heart of London, and under conditions where 

 no other species of this genus has been able to survive. It is 

 entirely due to the power of A^. stephensi to breed in wells, 

 covered cisterns, and such hke places, that it has been able to 



