Studies on the Breeding Places and Control ofAnopheles gambiaeandA. gambiaevar.melasin Coastal Districts of Sierra Leone

The eggs ofA. gambiaevar.melasare distinctly different from those of typicalgambiae, and it is now regarded as a distinct species,A. melas. Other workers have found that the larvae also differ, physiologically and structurally. All adults with an extra dark band on the palps—4-banded forms— are known to bemelas, but those adults with normal 3-banded palps can so far only be distinguished from typicalgambiaeby egg characters. A. melasis now known to be an important vector of malaria in coastal districts in West Africa. In some estuarine and mangrove swamp areas it may be even more important than typicalgambiae. Inmelascaught in Freetown estuary (mostly from Wellington village), 42 out of 1,000 glands dissected were positive, giving a sporozoite rate of 4·2 per cent. for all months of the year. The oocyst rate was 4·7 per cent., and the total infection rate was 7·8 per cent. In Freetown estuarymelasis rare in Freetown itself, and in the adjoining village of Kissy, but in all other parts of the estuary is at least as important as typicalgambiae. In many places it is the dominant vector. In Wellington to the east of Kissy, and on the Bullom shore which forms the north shore of the estuary,melasforms about 90 per cent. of Anophelines caught in houses.