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than in the thinly populated and jungly localities like Tengra. But throughout Calcutta, A nopheles 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 Circular Road. This area shows fewer A. rossi and culicines. It is noticeable that in Entally we get a sudden enormous increase of Culex 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 prevalent 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 larvæ 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. stephensi 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.