414 ANNUAL REPORT SMITHSONIAN" INSTITUTION, 1931 



discovery that yellow fever is conveyed from man to man by a 

 mosquito, the so-called tiger mosquito {Aedes aegypti or Aedes 

 argenteus or Stegomyia fasciata). This discovery greatl}'- increased 

 the activities of the students of mosquito biology. Yellow fever is 

 endemic to the Americas, but was established in west Africa some- 

 time before 1900.- Recent outbreaks in Africa have aroused world- 

 wide interest. Until 1928 it was confidently stated that only the 

 tiger mosquito was the vector of yellow fever. Bauer (1928) has 

 demonstrated that at least three other species may be vectors in west 

 Africa.^ Long before this (1879) Sir Patrick Manson had shown 

 that a round worm {FilaHa hancrofti) of man had a mosquito as 

 its host for part of its life cycle. It was not, however, till 1900 that 

 the method of transfer of this parasite was finally established. The 

 variety of diseased conditions produced in man by this parasite is 

 even yet not well known. This parasite is widespread throughout 

 the tropical and subtropical regions of the world. 



Dengue, a febrile disease of man which often appears in epidemic 

 form in the tropical and subtropical regions, was shown in 1903^ to 

 be transmitted by a mosquito {Culex fatigans). Recent work seems 

 to prove conclusively that Aedes argenteus^ the yellow-fever mos- 

 quito, and Aedes alhojnctus are the vectors. In addition to these dis- 

 eases of man, several animal diseases are transmitted by mosquitoes. 



The knowledge that mosquitoes are the vectors, and probably the 

 only vectoi-s, of these serious diseases of man has led to a world-wide 

 intensive study of mosquito biology. In 1900 some 242 species were 

 known from the world. To-day probably over 3,000 species are 

 recorded. All known species of mosquitoes pass their larval stages 

 in water. They are known to breed in a great variety of aquatic 

 environment — in ponds, slow-flowing streams, swamps, salt marshes, 

 pools formed by melting snows, all sorts of artificial water containers, 

 foul and clear water, reservoirs, rice fields, irrigation ditches, water 

 in tree holes, in the water contained by the leaves of epiphytic brome- 

 liads, in the water in the leaves of pitcher plants, etc. However, 

 from all these studies we are beginning to learn what are the aquatic 

 conditions essential for the breeding of each species of mosquito. 

 This has led to more intensive studies of certain species to determine 

 why certain types of aquatic environment are selected, and others, 

 apparently identical as far as we can judge, are avoided. It was 

 early recognized that not all types of water were selected by mos- 

 quitoes, but it was not till the past few years that attempts were made 



* It is now believed that yellow fever had its original home in Wt-st Africa and was 

 introduced into the Americas by the early navij,'ators and explorers. 



•At the present time (1932) at least 12 different specios of mosquitoes are known as 

 transmitters of yellow fever (7 species for Africa, 2 for South America, 2 for the Far 

 East, and 1, Aedes aegypti, of wide distribution). 



