ENTOMOLOGY 295 



diseases and related them to insect or arachnid vectors — such as 

 the work of Sir Ronald Ross and after him Sir Malcolm Watson 

 on malaria and mosquitoes, and of Sir Arnold Theiler and Louns- 

 bury on the diseases of animals. It is restricted to work on the insect 

 vectors of disease, and is intended to outline the recent advances in 

 parts of Africa by reference to some of the more striking publica- 

 tions of the past fifteen years or so. Some questions connected with 

 routine work on insect pests of man and animals, and the important 

 surveys of rats and fleas in connection with plague, are mentioned 

 in Chapters VIII and XVI. Apart from trypanosomiasis, the 

 diseases which have received most attention in respect of ento- 

 mological research are malaria, yellow fever, filariasis and relapsing 

 fever in men, and piroplasmosis (east coast fever) and infestation 

 by blowflies in animals. 



Diseases of Man 



By far the most important vectors of m^/flnVz are two species of mos- 

 quitoes, Anopheles funestus Giles and Anopheles gainbiae Giles. Both are 

 widely distributed with varying predominance, although Anopheles 

 gambiae is mainly responsible for the transmission of malaria in 

 East Africa and in Lagos. Research in recent years has been 

 mainly directed to investigations on the incidence of the disease 

 in various districts and to the control of the vectors themselves. 

 The mosquitoes are most readily controlled in the larval stage, but 

 effective control presupposes a fairly thorough knowledge of the 

 distribution of a given vector in relation to the incidence of the 

 disease, and of its bionomics, particularly its breeding habits. 

 Thus, Anopheles gambiae breeds in pools exposed to sunshine and 

 with little or no vegetation, whereas Aiiopheles funestus usually 

 breeds in clear water where there is some degree of shade. In 

 general, heavy shade makes conditions unsuitable for malaria 

 carriers (De Meillon 1933). Such information must be supple- 

 mented by detailed study of the bionomics of the species, with the 

 effect of local conditions upon them, and by statistical information 

 on their population, as is pointed out by Davey and Gordon (1933) 

 and by Anderson ( 1 93 1 ) . An ecological study of this type was made 

 by Hancock (1934). 



The correct application of suitable methods of sanitation con- 



