182 The Philippine Journal of Science 1915 
matter in the epidemiology of malaria in regions where rice lands 
are centers of population. 
While brooks or small rivers are preferred as breeding places, — 
Anopheles febrifer may occur in streams of very small flow. In 
one stream there was at that season no flow above ground, but 
the larve were found near the exit of a spring (Mindoro). They 
have been found in swamps, but only where there was a clear 
stream flowing over the swampy surface. 
While preferring shaded places, the larve are often found in 
brooks and ditches exposed to the sun, but only where there is 
some vegetation or other protection at the margin. 
The general character of the soil does not seem materially to 
affect the breeding of Anopheles febrifer. It has been found 
in brooks in the red soil of Bataan Province, in sandy streams 
of Pampanga, in streams worn in volcanic rock in Laguna, in 
the limestone region of Cebu, and in the stiff clay region of 
Mindoro. It has been found abundantly at considerable distances 
from any human habitation, and in ditches flowing between and 
under houses in large towns. 
The two localities in which Anopheles febrifer has been found 
most abundantly are two small rivers, one in southern Mindoro 
and one in Negros. In the latter locality, a clear brook with 
steep banks and much vegetation, sometimes between 100 and 
200 larvee could be taken up at one dip of a small collecting pan. 
The number of larve in a given part of a stream may vary 
from time to time, apparently independently of any change in 
conditions. This we have found to be the case in some streams 
at Canlubang, which we visited many times in the course of 
about five months for the purpose of collecting mosquitoes for 
feeding experiments. We found wide variations in the frequency 
of other species also. 
This species is sometimes found in association with Anopheles 
barbirostris in streams with abundant vegetation. It may often 
be found at the margin of a stream, while A. rossii is plentiful 
in alge at the center. We have sometimes found it in nearly 
“pure culture” at the steep shaded margin of a large brook, 
while A. barbirostris and A. rossii occurred at the more exposed 
margin at the other side. In a certain brook (Negros) A. 
febrifer was abundant at the margin, while A. rosszi alone 
occurred in carabao tracks containing water and exposed to the 
sun only a few centimeters from the margin of the brook. 
Fig. 1 shows the relative frequency of the larvee of four species 
of Anopheles in habitats arranged according to the amount of 
decaying organic matter in solution in the water. 
