2
than in the thinly populated and jungly localities like Tengra. But
throughout Calcutta, Anopheles rossi is very fairly prevalent, increasing much
in parts bordering on " Central Calcutta," like Entaliy, Circular Road and
Belgachia, and also some parts south of Park Street. By " Central
Calcutta " is meant the area north of Park Street and enclosed by the Circu-
lar Road. This area shows fewer A. rossi and culicines. It is noticeable
that in Entally we get a sudden enormous increase of Culew impellens and
fatigans during the months of January and February. These mosquitoes
tend to occur in such numbers as to make life almost unbearable. Other
species like the stinging Mansonioides and the huge Culex concolor, both
of which bite during daytime, add to the terrors of life. A similar increase
is noticeable in several of the southern and eastern suburbs of Calcutta, and
this sudden invasion of mosquitoes occurs at a time when the easterly winds
blow from the Salt Lakes. So far, the chief breeding areas of these species
have not been discovered and we cannot say whether they come from the Salt
Lakes or from the stagnations from the tanneries.
At other times of the year, Anopheles fuliginosus, jamesi, sinensis and
barbirostris, and also some rossi were commonly found in all the suburbs of
Calcutta. Near Kidderpore, A. listoni is also present, as also in Sibpur and
Ramkristopore on the other side of the river. The tank in the Campbell
Hospital is a source of a considerable number of A. fuliginosus and rossi in
varying proportions at different times of the year and occasionally some
listoni also.* In the Fort Maidan, the tanks breed A. fuliginosus and rossi;
and some of the ponds inside the Eden Gardens breed A. listoni besides. In
Sibpur and Ramkristopore the number of listoni (and also fuliginosus)
appears to have increased since last year. The beautiful ponds in the Royal
Botanic Gardens of Sibpur form large and fertile breeding grounds
principally for A. fuliginosus and sinensis. It has long been known that
malaria occurs in this neighbourhood, and the breeding places mentioned are
undoubtedly a contributory cause of infection.
Central Calcutta.—It is usually supposed that the central parts of
Calcutta are mostly free from mosquitoes other than the domestic species
like Stegomyia fasciata and observation shows that this is true. This is
because there are no breeding places other than the few ponds and tanks in
public squares and private houses; though in certain areas, cesspools and pits
afford suitable breeding places for Culex fatigans. The majority of the
mosquitoes that enter this area come from the outer regions of the city.
There is, however, one important exception this rule. Anopheles stephensi,
(a virulent carrier of malaria), has been found by the author to be very pre-
valent in Calcutta, even in its densely populated areas. This species has
been previously recorded from Calcutta by Stephens and Christophers as
early as 1902 (Reports to the Malaria Committee of the Royal Society). I
also learn that some specimens were bred out of larvae collected from an old
tub by Dr. U. N. Brahmachari and identified as A. stephensi by Christophers.
Up to now, no one appears to have suspected the fact that this dangerous
carrier of malaria is to be found breeding in large numbers throughout the
city and no doubt giving rise to a considerable amount of autochthonous
malaria among the population. The principal breeding places of A. ste-
phensi in Calcutta are the cisterns for storing filtered and unfiltered water on
the house-terraces. In every house in Calcutta, there is at least one cistern
for storing unfiltered water for use in flushing the lavatory; and in others
there are, besides, several cisterns for storing filtered water. Garden-tubs
and old unused cisterns also breed this species profusely. These cisterns
are the permanent breeding places of A. stephensi in the city, year in and
year out, though the percentage of infection of these cisterns increases during
and soon after the rains, i.e., August to October. Further, the temporary-
breeding places increase remarkably at the same time. Garden-tubs, old unused
cisterns and shallow pits on terraces form abundant breeding places. On
the third floor of a building near Dalhousie Square, a trough-like basin
(5' x 3' x 3") was formed as a result of the blocking of a small drain, in
*Some specimens of Anopheles albimanus were collected from this tank by Dr. U. N. Brahmachari.