SUNIER: Marine fish-ponds of Batavia. 205 
production of mosquitos was brought about. From the nature of the case 
a definite conjuncture of favourable conditions is required to render such 
an enormous production of mosquitos possible. But one of those conditions, 
indispensable to the appearance of such an enormous production of 
mosquitos, is the absence of the great numbers of kepala timah normally 
to be found in empangs; in other words the enormous production of 
mosquitos would not have taken place if the normally great number of 
kepala timah had been there. 
In my opinion the following words of WILSON (#7) are entirely applicable 
to the: Batavia empangs and to the part played in them by Haplochilus 
panchax (HAM. BUCH.): “That they” (scil. fish eradicating mosquito larvae 
and pupae) “play an important part in keeping down fly pests, such as 
“mosquitos, etc. is an-undoubted fact, and if it were not for their presence, 
“we would have millions of mosquitos where we have hundreds now”. 
Now once more summarizing my views on Haplochilus panchax (HAM. 
BUCH.) as an eradicator of mosquito larvae and pupae in the Batavia 
empangs, and referring the reader also to Chapter VI, I then start from 
the following facts: 
a. that the kepala timah, kept for a long time at my laboratory in various 
small aquaria which were in biological equilibrium and in which had 
been collected algae and higher submerged aquatic plants together 
with smaller animals such as Gammaridea, Copepods, Gladocera, 
Ostracods, Hydroporines etc. etc. from the Batavia empangs, regularly 
devoured with great avidity large quantities of Anopheline larvae and 
pupae; 
b. that in the alimentary canal of more than a hundred kepala timah 
whose intestine-contents I examined immediately after they had been 
caught in the empangs, I found, besides remains of various other 
smaller and occasionally somewhat larger (Nereidae) animals living in 
the empangs, invariably also larvae and pupae of Anophelines or 
remains of those; 
c. that Mr. VAN BREEMEN and I in the course of 18 months’ investigation 
of the empangs, ascertained twice — and that in open empang- 
water — a production of mosquitos far in excess of the usual Anopheline 
production of the empangs, determined by us quantitatively in 398 
cases; and that this enormous and abnormally high production of 
mosquitos both in the ponds of Heemraad Oost and in the little fry- 
pond near Pekulitan coincided each time with the total absence of 
Haplochilus panchax (HAM, BUCH.) which otherwise is regularly met 
with in large numbers in the Batavia empangs. 
From these facts I think I am warranted in concluding that there is 
more danger of the larvae and pupae eradicating action of Haplochilus 
panchax (HAM. BUCH.) being underrated than over-rated, and that the 
production of mosquitos by the Batavia empangs is kept down in a 
