33
which during the heavy rain sweep through the upper portion of the
district, never reach the lower part, the water being completely ab-
sorbed. In the gardens referred to the water supply is a difficult
problem, water having to be brought several miles in pipe lines from
the hills or obtained from deep wells sunk to a depth of from sixty to
ninety feet. At Gundarpara, one of these gardens, we found ano-
pheles in small numbers in the bungalow, but we failed to find any
source of these insects; at most of the other gardens in the same area
similar conditions existed. At Hantapara we caught M. listoni,
N. theobaldi and P. rossi; yet the only breeding places to be found
were a few small pools of waste water from taps, in which a very few
larvæ of P. rossi were found. During the height of the rains we found,
however, at a considerable distance a swampy freshet and at one end
of the very extensive lines a few pools of dirty water suitable for the
breeding of P. rossi. It may be suggested that in these cases anopheles
have been breeding in the hollows of large-leaved plants; but in the
Duars we have been unable to find larvæ in such situations and the
species found were the stream breeding M. listoni and puddle-breeding
P. rossi. At Binaguri, Lankapara, and Bandapani the same extra-
ordinary conditions occurred. It is of course possible that import-
ation may be partly responsible for these seemingly extraordinary
results; but the condition of residual anopheles, whatever be the
explanation of its occurrence in its different places, is an important
feature of the epidemiology of malaria in the Duars. It prevails
throughout the greater portion of the Duars when, as a result of
drought-a circumstance of constant occurrence during many months
of the year-breeding places have become very greatly reduced
in numbers; and it serves to keep supplied with anopheles aggre-
gations of human beings, however favourably they may be situated.
RESIDUAL MALARIA.
In the Duars some of the gardens are on comparatively high
land, some on land that can be described as almost waterless; others
on ground intersected in every direction with streams, and abound-
ing in springs and swampy places. The conditions as regards
facilities for the breeding of anopheles therefore vary very greatly
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