262 TREUBIA VOL. II, 2—4. 
in spite of the presence of swarms of the said larvae- and pupae- 
eradicating fish. stie 
On the contrary the conditions of life for the larvae of both species of 
Anophelines in the open water of the Batavia empangs are so unfavourable that, 
provided Haplochilus panchax (HAM. BUCH.) be present in sufficient 
numbers, this open water is practically free from Anopheline larvae !). 
The right of writing down the above words printed in spaced type I 
derive from the fact that by far the greatest production of Anophelines 
that Mr. VAN BREEMEN and I could observe in the Batavia empangs 
occurred as a matter of fact in ponds with entirely open water, absolutely 
clear of algal masses or other macroscopically visible water-plants and 
without any overhanging vegetation on the margins but from which 
Haplochilus panchax (HAM: BUCH) map pe nterd “Ho benennt ee 
absent. 
The ponds in question are situated near Heemraad Oost. On October 
22nd 1918 these ponds were still quite dry. They had then been dry 
already for some considerable time, so that all the aquatic plants and 
animals had perished or disappeared and the bottom of the pond had 
cracked in many places. On November 13th following Mr. VAN BREEMEN 
saw that these ponds contained water again. Both kepala timah and algal 
masses or higher water plants were entirely missing, yet the ponds were 
absolutely teeming with mosquito larvae. 
On November 18th I also visited these ponds and I could personally 
ascertain the facts, that the ponds contained no algal masses or higher aquatic 
plants and no Haplochilis panchax (HAM. BUCH.), but were still swarming 
with huge numbers of mosquito larvae and pupae, which, together with 
many empty pupa-skins had been driven together by the wind so as to 
form a dense strip along the lea-edge of the ponds. 
The salinity in these ponds was in three different places 35.3; 40.7 
and 25.0°/ 9). On the spot where the salinity was 25.0°/,, and where great 
masses of larvae, pupae and empty pupa-skins had been driven together 
in a corner of the pond by the wind, four mosquito-nets were set on 
November 14th, 1918. Next morning the contents of these four nets were 
examined by Mr. VAN BREEMEN and his staff. 999 Female Anophelines 
were then determined. Five of these were Myzomyia ludlowi THEOBALD, 
the remaining 994 being Myzomyia rosii GILES. The whole contents of 
the nets may be tabulated thus: 
!) In this connection the following fact also seems to me significant, In empangs 
containing floating algal masses and higher submerged plants reaching up to just 
beneath the surface of the water, the mosquito larvae and pupae in the open water 
that have not been gobbled up by Haplochilus panchax (HAM. BUCH.) are continually 
driven together by the wind into the protecting milieu of those conglomerates of aquatic 
plants and of the marginal plants projecting partly into the water. Moreover the larvae 
concentrate actively into places of protection like surmerged aquatic plants reaching 
the water surface, overhanging land plants projecting partly into the water, floating 
débris etc. The latter fact has already been observed by HILDEBRAND (*). 
