The record-union., 1899-10-16

courses, and temporary pools of rain
water. So far as / have yet observed
the larvae are seldom to be found in
larger bodies of water, such as tanks,
rice fields, streams and rivers and lakes,
because in such places they are de-
voured by minnows and other small
fish Nor have l ever seen any evil
dence in favor of the popular view that
they breed in damp grass dead leaves
and so on.
Hence in order to get rid of these in
sects from a locality, it will suffice to
empty out or drain away, or treat
with certain chemicals, the small col
lections of water in which their larvae
must pass their existence.
CAN WE GET RID OF THE IN
| SECTS?
But the practicability of this will de-
pend on circumstances-esp specially, I
think, on the species of mosquito with
which we wish to deal. In my expert
ence, different species select different
habitations for their larvae. Thus the
common "brindled mosquitoes" breed
almost entirely in pots and tubs of wa
ter; the common gray mosquitoes
only in cisterns, bitches and drains;
while the rarer "spotted-winged mos
quitoes seem to choose only shallow
rain water puddles and ponds too large
to dry up under week or more, and
too small or too foul and stagnant for
minnows.
Hence the larvae of the first two va
rieties are found in large numbers
round almost all human dwellings in
India and, because their breeding
grounds-namely, vessels of water,
drains and wells-are SO numerous and
are SO frequently contained in private
tenements, it will be almost impossible
| to exterminate them on a large scale.
THE DANGEROUS KIND OF IN
SECT.
| On the other hand, spotted-winged
mosquitoes are generally much more
rare than the other two varieties. They
| do not appear to breed in wells, ciS-
terms and vessels of water, and there
fore have no special connection with
human habitations. In fact it is usually
a matter of some difficulty to obtain
| their larvae. Small pools of any per-
manence-such as they require-are not
common in most parts of India, except
during the rains, and then pools of this
| kind are generally full of minnoWs
which make short work of any mos
quito larvae they may find. In other
words, the breeding grounds of the
spotted winged varieties seem to be so
isolated and small that l think it may
be possible to exterminate this species
under certain circumstances.
THE SPOTTED WINGED.
The Importance of these observations
/ will Hn rxTbn + hOf
hitherto the parasites Of human malaria
have been found only in spottedwinged
osquitoes-namely, in two species Of
them in India and in one species in
Italy AS a result of very numerous ex-
periments I think that the common
brindled and gray mosquitoes are quite
innocuous as regards human malaria
Ia fortunate circumstance for the hu-
man race in the tropics. And Professor
Grassi seems to have come to the same
conclusion as the result of his inquiries
in Italy.
But I wish to be understood as writ
| ing with all due caution on these points.
! Up to the present our knowledge, both
as regards the habits of the various
species Of mosquito and as regards the
capacity of each for carrying malaria,
is not complete. All I can now say is
that if my anticipations be realized-if
| it be found that the malaria bearing
species of mosquito multiply only N
small isolated collections of water
which can easily be dissipated-we shall
possess a simple mode of eliminating
malaria from certain localities.
WHERE THEY BREED.
I limit this statementAto certain To-
calities only, because it is obvious THAI
where the breeding pools are very num-
erous, as in water-logged country, or
where the inhabitants are not suffi.
GENTLY advanced to take the necessary
precautions, we can scarcely expect the
recent observations to be of much use
at least for some years to come. And
this limitation must, / fear, exclude
most of the rural areas in India.
BENEFIT OF THE DISCOVERY.
Where, however, the breeding pools
are not very numerous, and where there
is anything approaching a competent
sanitary establishment, we may,
think, hope to reap the benefit of these
discoveries. And this should apply to
the most crowded areas, such as those
! or cities, towns and cantonments, and
also to tea, coffee and indigo estates,
and perhaps to military camps.
For instance, malaria causes an enor-
nous amount of sickness among the
poor in most Indian cities. Here the
common species of mosquitoes breed in
the precincts of almost all the houses
and can therefore scarcely be extermi-
mated; but pools suitable for the spot
ed-winged varieties are comparatively
scarce, being found only on vacant
areas, ill-kept gardens, or beside roads
in very exceptional positions where they
can neither dry up quickly nor contain
fish. Thus a single small puddle may
supply the dangerous mosquitoes to
several square miles containing a
crowded population; if this is detected
and drained off-whch Will generally
cost only a very few rupees-we may
expect malaria to vanish from that par
ticular area.
DANGER IN A PUDDLE.
The same considerations will apply
to military cantonments and estates
under cultivation. In many such ma
laria causes the bulk of the sickness,
and may often, / think, originate from
two or three small puddles Of few
square yards in size. Thus in a ma
larious part of the cantonment of Sc
cunderabad, found the larvae of spot
lted-winged mosquitoes only after long
search in a single little pool which
could be filled up with a few cart-loads
of town rubbish.
In making these suggestions I do not
wish to excite hopes which may ulti-
| fp1r 40 hox al