190 
Malaria in Malaya 
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find infected females of aconita , only reputedly bad vectors, like sinensis , 
barbirostris, indefinita, and fuliginosus, were found infected. M. aconita was 
often found in districts where the incidence of malaria was insignificant. 
Attempts at experimental infection rarely succeeded (Schiiffner). It seems 
therefore, that the infectivity of this species is subject to considerable variation, 
and its importance depends, to a large extent, on its occurrence in large numbers 
and throughout the year. If present in scanty numbers, or within the limits 
of particular seasons, it may cause epidemics of greater or less severity, but 
it does not seem to be capable of permanently raising the splenic index 
distinctly, as is the case with M. ludlowi, notwithstanding that the latter 
species shows a marked seasonal prevalence, and may be absent for a whole 
year. Although the importance of M. aconita should not be underrated, it is 
negligible in comparison with M. ludlowi. 
3. N. maculatus. Infected specimens were never found, though sought 
for in highly malarious regions, where M. sinensis and N. fuliginosus showed 
infection (Soendatar), but the numbers examined were too small to allow of 
any definite conclusions being reached. On the other hand, the indirect index 
often points it out as a dangerous species, for its absence or presence in 
neighbouring districts, which otherwise possess a similar Anopheline fauna, 
coincides with the absence or presence of severe malaria. There are exceptions 
to this rule, however: in Siboga N. maculatus prevailed in the hills, while 
malaria was mainly confined to the seashore (M. ludlowi). 
Here again, as with M. aconita, we must infer a high degree of variability 
in the power to rear malaria parasites on the part of the vector. 
4. N. leucosphyra. Schiiffner and Swellengrebel (1914) observed a distinct 
correlation between the appearance of this species and local outbreaks of 
malaria on tobacco estates and in certain coolie lines. Similar observations 
have been recorded by Roper (1914). Recently, Bais (1919) has confirmed 
and extended these observations by finding infected specimens (N. I. = 1-7 
per cent.). He also succeeded in attempts at experimental infection with 
tertian parasites, the rate of infection, however, not surpassing that of 
M. sinensis as observed by us in some of our experiments (50 per cent.). 
5. M. sinensis and N. fuliginosus. Both of these species were found 
infected in malarious regions, the former commonly so, but the N. I. was 
uniformly low (under 1 per cent.). Experimental infection of M. sinensis 
with tertian succeeded to a fairly high degree (at times over 50 per cent.); 
infections with subtertian and quartan were rarely successful. Experimental 
infection in man (with the same precautions as those taken with M. ludlowi) 
succeeded twice. N. fuliginosus was infected experimentally by Schiiffner 
with subtertian (4 per cent.). The two species are common in both malarious 
and salubrious regions; in the former case obviously infected carriers are 
frequent. But in Soendatar, a region of severe malaria, we found them 
