264 TREUBIA VOL II, 2—4. 
were entirely absent as the production of the entire pond, that production 
is still enormous. 
This becomes apparent on a comparison of the quantity of rossii 9 © 
produced in the present case by the open empang-water, with the largest 
catches among the 398 made by us above the submerged vegetation, also 
of rossii 22. 
In Tables V and VI the reader finds the quantitative results of all the 
catches by mosquito nets expressed in the numbers of /zdlowi and rossii Q 2 
captured per night and per 10 M?. In the case discussed above the open 
pond-water produced per 10 M? and per night —- i = = 17288 rossii 9 ©, 
Now taking the view that the mosquito- are and pupae had been driven 
together by the wind within '/,, of the pond-area and therefore dividing the 
catch by 10, even then this catch of rossii QQ made over open pond- 
water in a pond destitute of kepala timah remains considerably higher 
than the biggest catch of the same mosquitos, out of 308 catches made 
above the submerged vegetation in ponds in which Haplochilus panchax 
(HAM. BUCH.) did occur. This biggest catch referred to amounted to 1466 
rossii 99 per 10 M? and per night (cf. the Tables IV, V and VI; November 
24th 1918, Jaagpad). As regards the /udlowi QQ, the biggest of 398 catches 
amounted to 648 99 per 10 M? and per night (cf. Tables IV, V and VI, 
July 25th 1919, Heemraad) !). 
Our observations discussed here concerning the ponds near Heemraad 
Oost are not isolated cases. Already on October 15th 1918 Mr. VAN 
BREEMEN had discovered near Pekulitan a little bandeng fry pond containing 
no kepala timah and practically no water-plants. The fact is that from a 
bandeng fry pond the rearers remove not only all kepala timah, which would 
devour the bandeng fry, but frequentiy also the water-plants or at least the 
bigger algal masses, as the young fry gets entangled in dense algal masses 
such as are formed especially by Chaetomorpha. The open water of this 
little fry pond perceived by Mr. VAN BREEMEN near Pekulitan, in which kepala 
timah therefore was not present, as a matter of fact swarmed with larvae 
and pupae of Anophelines and other Culicidae. Similar huge masses of 
mosquito-larvae and -pupae were observed by us only in the ponds of 
Heemraad Oost just discussed and likewise destitute of kepala timah, but 
never in ordinary empangs containing the normally very great numbers 
of kepala timah. 
Now it will not do to conclude that it is only in consequence of the 
absence of kepala timah in the cases here described that the enormous 
DE It i is self-evident that the fact of the enormous numbers of Anophelines pro- 
duced in the above case by the open pond-water consisting, at least as regards the 
females, for 99!/,°/) of Myzomyia rossii GILES and only for 17,0, of Myzomyia ludlowi 
THEOBALD, has no bearing on the significance of this case for judging of Haplochilus 
panchax (Ham. BUCH.) as an eradicator of mosquito-larvae and -pupae. Either the 
natural conditions in the ponds in question were more favourable to the larvae of rossii 
than to those of ludlowi, which as we shall see below is quite possible, or far more rossii 
than /udlowi [9 laid their eggs in the ponds in question after these had been replenished. 
