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Effective and safe mosquito repellants that do not hurt the environment would be a welcome addition in the battle against diseases such as malaria, West Nile virus, encephalitis and yellow fever. Researchers may have found such a weapon that is produced by an insect called the backswimmer (Notonecta maculata).
Backswimmers like to eat mosquitoes. Scientists have known that mosquitoes avoid water where backswimmers live and mosquitoes will not lay their eggs in this water. However, the chemicals produced by backswimmers and detected by mosquitoes had not been identified until now. The researchers identified two chemicals (n-heneicosane and n-tricosane) in air samples collected directly over water where backswimmers lived and tested these chemicals for their ability in reducing egg laying by mosquitoes.
Water treated with n-heneicosane and n-tricosane reduced mosquito egg laying by 65% on the first night. Water samples where backswimmers lived reduced mosquito egg laying by a similar amount. Although backswimmer water was effective for several days, water treated with n-heneicosane and n-tricosane did not prevent egg laying on the second day of testing.
These data suggest that mosquitoes can detect chemicals released from backswimmers and will avoid laying their eggs in water containing these chemicals. Mosquitoes that avoid this water will not get eaten by the backswimmers, but they will not lay their eggs in this water. Therefore, they might get eaten by other animals or die as they look for other places to lay their eggs.
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