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Malaria is transmitted between people by female Anopheles mosquitoes, and more than 60 species have been incriminated in the transmission of infection (there are about 430 species of Anopheles, and about 3500 species of mosquitoes altogether).
Some species are more significant than others as vectors because of variations in susceptibility to the parasite or the propensity of the mosquito to bite humans and to enter houses when looking for a blood meal. Anopheles gambiae sensu lato is the vector of most significance in Africa.
Both male and female mosquitoes feed on nectar and damaged fruits. But only females feed on animal blood to provide proteins for their eggs. The adult mosquito survives for between one week and one month.
Females lay their eggs in batches of 70-100 on the surface of water at night. The type of water used for egg laying is indicative of the mosquito species and includes irrigation channels, a pool of water in a tree trunk, and sewage effluent. In tropical temperatures the eggs hatch after two to three days.
The larvae lie just below the surface of the water and feed on algae, and after 7-14 days turn into pupae during a five-minute process. The pupa is comma-shaped and is the least active stage of the Anopheles lifecycle. After two to four days the pupa metamorphoses into an adult mosquito. The adults emerge during late evening and are able to fly within minutes.
Mosquitoes usually mate during flight. The male is attracted to the female by the tone of her wing beat, and has antennae that act as sound receptors. Once mated, the female searches out a blood meal, following sensory cues such as host odour, carbon dioxide and convection currents. She then seeks out a resting place, which may be indoors or outdoors depending on the species.
When the blood meal has been digested, the ovaries develop and the mature eggs are laid at night.
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[WTD023872] The life cycle of Anopheles mosquitoes.doc