192 
Malaria in Malaya 
II. Habitats of the Anopheline Larvae. 
One of the conditions needed for the institution of specific sanitary 
measures, appears to hold in the Malay Archipelago. In all highly malarious 
districts studied hitherto, only one or two species are certainly or presumably 
principal vectors, and the remainder may be neglected. But are we justified 
in neglecting them? Is it possible to carry out sanitary works, directed against 
these known vectors, without including all other Anophelines in that locality? 
In other words, are the breeding-places of known vectors sufficiently differen¬ 
tiated to allow of “specific sanitation” (see p. 181)? This problem we must 
solve, otherwise our measures may prove useless. 
A species may be particular in the choice of its breeding-place, or on the 
other hand it may show a considerable degree of adaptability in this respect. 
When observations are conducted in but one locality, it is often impossible to 
form a correct opinion on this subject, even after prolonged investigation. 
In the course of observations lasting nearly a year, we found (in Modjowarno, 
East Java) the larvae of M. aconita inhabiting rice-fields exclusively, and 
usually fields about to be harvested. In other localities this species was found 
to be more generally distributed (see Table V, p. 194). 
The larvae of N. maculatus were found only in hilly districts, they are 
generally confined to little streams and springs on hill slopes. Consequently 
it might be supposed that sub-soil drainage, etc. would eliminate the larva. 
Unfortunately, we have noted abundant larvae of this species in a variety 
of waters (rice-fields, puddles, brackish pools near the seashore, cement tanks, i 
etc.) during the dry season when the small streams above alluded to are dried 
up (see Table V). 
The larvae of M. unibrosus occur in fresh and brackish water near the 
seashore and elsewhere, showing a preference for shade, but sometimes occurring 
in the open with no other protection against the sun than that afforded by 
short rushes. The larvae of N. leucospihyra on the other hand invariably 
affect shady pools, without discrimination in other particulars, the water 
being clean or muddy, stagnant or running. Our observations regarding the 
latter species are few (see Table Y). 
The larvae of most of the other species occur in a variety of waters. 
Some, like M. aconita, select one particular type, almost to exclusion of others, 
in Mandailing for instance, we found larvae of M. barbirostris frequenting 
fish-ponds, but comparatively rare in the rice-fields, where M. sinensis was 
the commonest larva. In other localities, however, M. barbirostris larvae were 
even more numerous in the rice-fields than were those of M. sinensis. This 
observation also applies to other species which are very particular in their 
choice of a breeding-place; in other districts they appear to be independent 
of special breeding grounds (see Table V). 
A few species never leave us in doubt as to their dependence on particular 
breeding-places; some species are ubiquitous— N. annulipes var. moluccensis 
