2°3 
Chaffer XX 
The Relation of Species of Anophelinae to 
Malarial Endemicity 
Species undoubtedly play an important part in 
the development of blood parasites in the mosquito. 
Proteosoma , for instance, develops in certain 
species of Culex , e.g., C. nemorosus was used by Koch 
in Europe. It does not, however, develop in certain 
species of P aeniorhynchus (S. P. James). 
The malaria parasite does not develop in species 
of Culex , Paeniorhynchus, Stegomyia , or other blood¬ 
sucking flies, e.g., Phlehotomus, Simulium , etc. In the 
case of Culex fatigans placed under absolutely identical 
conditions with Anofihelines, no sign of zygote formation 
occurs on the second or third day. 
Similarly with regard to Filaria , it is only in 
certain species of Culicidae that certain species of 
Filaria will develop, thus Ce. argyrotarsis is an efficient 
host for F. hancrofti , but inefficient for F. demarquaii. 
The malarial endemicity or endemic index may be 
defined as the percentage of infected children (under 
ten years of age) in any district, and represents the 
liability of-immigrants to contract malaria. 
It is well known in a general way that in one 
country malaria is more intense than in another, but 
here we have a means of exactly measuring this differ¬ 
ence, and, moreover, in the different parts of any 
particular district. We may illustrate this by the 
differences we found in Bengal in an extent of country 
where, as far as we could judge, the climatic conditions 
were practically identical, yet we find in the environs 
of Calcutta the endemic index is o, while in the Duars 
