SUNIER: Marine fish-ponds of Batavia. 259 
data concerning the magnitude of the production of Anophelines by the 
Batavia empangs per unit of surface-area and per night. 
As I had occasion to mention before, our mosquito-nets were always 
set in those places in the Batavia empangs where the submerged vegetation 
described in Chapter IV and illustrated in our photos 2, 3, 4, 6, 8, 9, 14 and 15 
(Plates VII, VIH, IX, Xi, XIV, XV, XXII, and XXIII) had developed more 
or less luxuriantly. With a single exception therefore, to which I will refer 
again later on, the nets were not set on open pond-water. 
As a matter of fact the open water of the Batavia empangs is practically 
free from Anopheline larvae. As early as 1908 KIEWIET DE JONGE (?) 
wrote: “thus the larvae” (sc. Anopheline larvae) “are found there” (sc. in 
the Batavia empangs) “especially in and among the numerous conglomerates 
“of water-plants floating there”. VAN BREEMEN (°°) also says that in 1917 
and 1918 he learned from observation that in the empangs “the Anopheline 
“larvae chiefly lurked in the algae floating at the surface of the water and 
“in the vegetation of higher aquatic plants growing up to the surface, 
“which water plants enable the larvae to hold their own in the struggle 
“with the larvae- and pupae-devouring fishes”. Further down in the same 
article VAN BREEMEN (°°) says once more that “in normal circumstances 
“the open water is free from mosquito-larvae owing to the presence of 
“kepala timah” (= Haplochilus panchax (HAM. BUCH.), cf. Chapter VI). 
It is a recognised fact that here in the tropics it is generally speaking 
open water alone that can be kept practically free from mosquito-larvae 
and -pupae by the presence of a sufficient number of fish preying on 
those larvae and pupae. Thus the following passage is met with in the 
well-known “Handbuch der Tropenkrankheiten” by MENSE (°°) (Volume V, 
p. 439) in the Chapter on malaria prophylaxis, where the “Feinde der 
Mückenlarven aus Pflanzen- und Tierreich” are discussed: “Fische scheinen 
für manche Gewässer eine ziemliche Bedeutung zu gewinnen, aber nur 
wenn sich kein starker Pflanzenwuchs darin befindet und die Ufer steil 
ansteigen, da anderenfalls die larven zu viel Schutz finden”. (This passage 
has already been quoted on page 235). 
WILSON (#7) also says: “When introducing fish into ponds for purposes 
“of destroying mosquito larvae, it is necessary to conserve such waters by 
“the removal of surface weeds and floating débris near the margins and 
“draining or filling in isolated pools near the foreshore. The value of 
“this conservancy became apparent to me during my earliest experiments 
“with fish as larvicides. The ponds which were selected for the first 
“experiments were comparatively clear of surface weeds and floating débris 
“and mosquito larvae could be found near the margin. They were stocked 
“with larvae-eating fish and after a few days were thoroughly examined, 
“with the result that no larvae could be traced excepting above some 
“patches of surface weed; this weed was promptly removed and a further 
“search was made the following day with a negative result. 
