162 
MALARIA 
ure of oocysts to develop in experimental 
or wild caught anophelines). A new epi¬ 
demic may occur if a heterologous strain 
is introduced or a more susceptible anoph- 
eline transmitter invades the region. 
However we have certain anophelines that 
seem almost perfect transmitters, as A. 
gambiae ( costalis ), and epidemics follow its 
introduction into an endemic region. 
As pointed out in the beginning, of the 
nearly 200 anopheline species in the world, 
scarcely more than a score are known to be 
efficient or * ‘ dangerous ’ ’ transmitters. Ex¬ 
perimental work indicates that all anophe¬ 
lines, so far as tested in any numbers, have 
a high degree of susceptibility to infection. 
If this is true, why should we not have more 
intensive malaria transmission? Recent 
work in many lands and by many workers 
has demonstrated that many of our anophe¬ 
lines are not androphilic. Furthermore, it 
has been demonstrated that in one of our 
best known anopheline transmitters (A. 
maculipennis of Europe) there are several 
distinct races or sub-species, only two or 
three of which are androphilic. 
