182 
Malaria in Malaya 
(1) The species of Anophelines that are the principal vectors. 
(2) The habitats of the larvae of these Anophelines. 
Although it has been shown that'the Anopheline fauna of the Peninsula 
and Archipelago are practically identical, we had doubts from the start, as to 
the advisability of applying without further investigation the results obtained 
in the Peninsula. This cautious attitude has proved to be justified. 
In the following we shall constantly allude to the results of other investi¬ 
gators in the Malay Archipelago—Schiiffner, v. Breemen, Bais, Citroen, and 
Winoto. 
I. The Principal Vectors of Malaria in the Malay Archipelago. 
At the commencement of our inquiry (February, 1917), data relating to 
this subject with respect to our Colonies, were scanty. Schiiffner (1902) and 
de Vogel (1909) had succeeded in infecting mosquitoes, but unfortunately 
some doubt exists as to the species with which they experimented. We regard 
it as highly probable that Schiiffner experimented with M. ludlowi, and de 
Vogel with M. rossii. As regards the Malay Peninsula, our information was 
moie extensive, comprising, as it did, the results of the researches of Watson 
(1911), Stanton (1914), and Strickland (1916). We are also acquainted with 
the work of Walker and Barber (1914) in the Philippine Islands, and with 
that of Kmoshita (1906) in Formosa. Barber’s paper (1918) made its appear¬ 
ance some months after the publication of our first paper. The authors I have 
cited indicate iff. umbrosus , N. maculatus , iff. aconita, iff. minima {febrifer), 
and iff. sinensis as the most dangerous species, but none of them appears to 
consider iff. ludlowi as an important vector, although Christophers long ago 
proved it to be such in the Andaman Islands. Stanton is dubious on the 
subject, while Watson (1915, pp. 82-83) remarks “My feeling from what I have 
seen in the Federated Malay States is, that A. ludlowi can exist, without 
producing malaria, and indeed that malaria will disappear from a place where 
steps are taken which abolish only A. umbrosus —a proved carrier, yet leave 
very large numbers of A. ludlowi .” Strickland considers it to be of importance, 
but only if it is very plentiful, contrary to the hill species which remain 
dangeious even when scanty. These opinions are interesting in the light of 
our own findings, which showed iff. ludlowi to be the most important vector 
of all the Archipelagan species. This shows the indispensability of local 
researches. Had we neglected them by simply accepting the results obtained 
in neighbouring countries, we should have fallen into grave errors. 
Whether or not a certain species is a good vector may be determined by 
(a) the direct and (b) the indirect method. For the present we shall consider 
the direct method only. This consists in determining the rate of infection with 
malaiia parasites (a) in mosquitoes fed on gamete carriers (rate of experi¬ 
mental infectability or shortly “E. I.”) or (b) in mosquitoes caught in nature 
(rate of natural infectability, in short “N. I.”). Of the two methods, the first 
has found a much larger application, because it is more generally practicable. 
