260 TREUBIA VOL. II, 2—4. 
“The margins of ponds, etc. should be trimmed and over-hanging 
“plants that reach to the surface of the water should be cut back, as these 
“tend to hold up débris and protect the larvae. All small isolated puddles 
“should be filled in or drained”’. 
In Chapter VI when discussing the food of the kepala timah (Haplochilus 
panchax (HAM. BUCH.)), I pointed out that MENSE (°°), WILSON (77) and 
SEYMOUR SEWELL and CHAUDHURI (**) count certain species of Haplochilus, 
among which Haplochilus panchax (HAM. BUCH.), among the best destroyers 
of mosquito-larvae and pupae, and that it even became apparent to 
SEYMOUR SEWELL and CHAUDHURI (%) from comparative experiments that 
these species of Haplochilus are still far better larvicides than the famous 
millions (Girardinus poeciloides DE FILIPPI) of Barbados. 
Nevertheless, as I already stated in Chapter VI, in spite of the continu- 
ous presence of very great numbers of Haplochilus panchax (HAM. BUCH.) 
there, the Batavia empangs teem with larvae and pupae of Myzomyia 
ludlowi YHEOBALD and Myzomyia rossii GILES, in those places where 
masses of algae float at the water-surface, or more generally, where the 
submerged vegetation reaches the surface of the water and sometimes 
also where the over-hanging land-plants touch the surface of the water 
or even (Paspalum distichum L.; cf. Chapter 1) extend their growth 
along the pond-bottom when the latter is covered by very little water 
only. 
The chief factor seems to be that the submerged algae and higher 
water-plants floating at or reaching up to the surface of the water together 
with the over-hanging land-vegetation of the pond-margin touching the 
water-surface, protect the eggs, larvae and pupae of the mosquitos more 
or less from the animals preying on those eggs, larvae and pupae, these 
animals being in the first place Maplochilus panchax (HAM. BUCH.). Most 
authorities are agreed as to the correctness of this view, as may appear 
from the above-quoted sentence from MENSE (°°). WILSON (37) also states 
that “surface weeds etc. protect the larvae from their enemies”. 
Further HILDEBRAND (°°) writes: “Algae often form mats which float 
“at or near the surface. Mosquito larvae, particularly us. find PEN 
“from fish over and in these mats. 
“The aquatic plant, Najas flexilis, mio was common in See 
“ponds, forming a dense growth over the bottom, normally does not provide 
“protection, as it does not reach the surface of the water. During the severe 
“fall drought the water, hoewever, became so low that it was near the 
“surface or partly exposed in many places, making such a dense mass that 
“fish could not penetrate it. Wherever this occurred it furnished excellent 
“protection and Anopheles larvae and pupae were common. 
“Nearly all marginal plants, by projecting partly into the wter. = 
falling into it after maturing, or by becoming partly submerged after freshets, 
furnish protection for mosquito larvae. 
