N. H. SWELLENGREBEL AND J. M. H. SwELLENGREBEL-DE GrRAAF 197 
On the other hand, whenever the species occurs in well-cultivated rice- 
fields, nothing at present can be done to prevent its propagation. 
The larval habitat of the “littoral” M. ludlowi, on the contrary, facilitates 
sanitary measures; also, the “inland” form may be exterminated by the 
abolition of fish-ponds. Without improvement in the methods of rice cultiva¬ 
tion, however, little can be accomplished. 
CONCLUSIONS. 
1. The eradication of Anopheline larvae, in the Malay Archipelago, is 
difficult because they breed in all kinds of temporary collections of water, 
which constantly reappear throughout the rainy season. 
2. Anti-larval measures directed against M. aconita and N. maculatus are 
hard to carry out; specific sanitation is rendered difficult by their breeding 
habits, but amelioration may be expected as the result of improved methods 
of rice cultivation. 
3. Specific sanitation is practicable in malarious regions where M. ludlowi 
is the chief vector. 
The observations detailed in this paper might lead to the supposition 
that, in the Malay Archipelago, our investigations have been more academic 
than practical. This is not so. In several places on the sea shore (Siboga, 
Belawan in Sumatra, Batavia, Tegal, Semarang, Soerabaia, Tjilatjap in Java), 
and in some localities of minor importance in the interior, anti-malarial 
operations are in progress, or in preparation, but years must elapse before we 
can appreciate their effect. Where a distinct amelioration has been observed 
(e.g. Siboga) we are uncertain as to whether this should not be attributed to 
a remission in the intensity of endemic malaria, so frequently observed in the 
Malay Archipelago. So soon as conclusions may be drawn regardin'* the 
1Y» . J ob 
efficacy of our sanitary measures, we hope to make them known. 
REFERENCES. 
Note. Some citations in the text are to unpublished Official Reports by Reylingh, 
Schiiffner and Swellengrebel respectively, bearing dates from 1916 to 1919. 
Barber (1918). Some observations and experiments on the Malayan Anopheles, with 
special reference to the transmission of malaria. Philip. Journ. of Sci. Sect. B, xm. 1. 
Breemen, van (1918). De verbreiding van de malaria in Weltevreden en Batavia. Geneesk. 
tijdschr. v. ned. Indie, lviii. 623. 
— (1919). Verdere gegevens betreffende het malaria vraagstuk te Weltevreden en Batavia. 
Ibid. lix. 311. 
Citroen (1917). Anophelinensoorten te Soerabaia. Ibid, lvii. 763. 
Kinoshita (1906). fiber die Verbreitung der Anopheles auf Formosa und deren Beziehung 
zu den Malaria Krankheiten. Arch. f. Schiffs- u. Tropenhi/giene, x. 621, 676, 708, 741. 
Roper (1914). An account of some Anopheline mosquitoes found in British North Borneo. 
Bull. Entomol. Research, v. 137. 
