x%,B3 © Barber et al.: Malaria in the Philippines Si 
the apparently pure salt water of the inflowing tide at the mouth 
of a river (Tayabas). It is very often associated with A. rossii 
in masses of alge exposed to the sun, especially in rivers. 
Anopheles febrifer is more restricted in habitat than either 
of the foregoing species. We have never found it in brackish 
water. It shows a decided preference for clear flowing water, 
especially where there is an abundance of overhanging grass, 
roots, or other vegetation at the margin. It is rarely found 
except at the banks of the stream or at the edges of islets of 
grass or the like, and when liberated in the center of the stream 
the larve usually wriggle rapidly to the shaded margin. It 
prefers brooks and small streams to large rivers, although it 
may sometimes be found at the margins of the latter, especially 
if a steep bank or grass or other vegetation offers shelter. It 
often occurs in small indentations in the shore or along the 
banks of slightly widened parts of a stream where quieter water _ 
is found. It almost never occurs where a current strikes the 
banks; small dams, often made in small streams to obtain a pool 
for laundry purposes, afford a favorite shelter. Although pre- 
ferring vegetation at the margin of a stream, Anopheles febrifer 
may sometimes be found on a bare clay bank, especially if it 
is slightly overhanging. We have found it in small numbers 
among stones at the margin of a river (Palawan) and on stones 
at the walled sides of ditches in the streets of a town (Lilio). 
This species tends to avoid the presence of decaying vegetation 
in water beyond a certain degree. It is usually absent in small 
bayous of half a meter to a few meters in length, extending from 
brooks in which it is abundant. Where a brook broadens to a 
width of a meter or more, offering quiet water at the margins, A. 
febrifer is often found abundantly, but if the stream widens to a 
broad pond, the larvee become rare or absent. Where the same 
brook becomes swiftly flowing again, the larve reappear. We 
have not found them in pools or ponds without outlet. A certain 
amount of sewage or other animal matter in water is tolerated. 
We have found the species abundantly some rods below the exit 
of a large septic tank (Canlubang), but not immediately below. 
It also occurs, often in considerable numbers, in ditches serving 
as open sewers, these containing clear water with a small amount 
of sewage. We have found it in a brook into which water was 
seeping from pits containing soaking hides (Magdalena). Al- 
though usually found in clear water, it may occur in brooks 
rendered turbid by carabaos (Cebu). Anopheles febrifer has not 
been found in rice paddies, and the flow of water over extensive 
rice paddies seems to unfit it for this species—a very important 
