According to the World Health Organisation, malaria, a disease spread by mosquitoes, affects millions of people every year. Everyone knows how irritating the noise made by a mosquito, (13) by a painful reaction to its bite, can be. It is astonishing that so (14) is known about why mosquitoes are drawn to or driven away from people, given (15) level of distress and disease caused by these insects. We know that the most effective chemical (16) protecting people against mosquitoes is diethyltoluamide, commonly shortened (17) deet. (18) deet works well, it has some serious drawbacks: it can damage clothes and some people are allergic to it.

Scientists know that mosquitoes find some people more attractive than others, but they do not know (19) this should be. They also know that people vary in (20) reactions to mosquito bites. One person has a painful swelling while (21) who is bitten by the same mosquito (22) hardly notice. Scientists have (23) discovered the reason for this, but they have carried (24) experiments to show that mosquitoes are attracted to, or put (25) by, certain smells. In the future, scientists hope to develop a smell that mosquitoes cannot resist. This could be used in a trap (26) that, instead of attacking people, mosquitoes would fly into the trap and be destroyed. For the time (27) however, we have to continue spraying ourselves with unpleasant liquids if we want to avoid getting bitten.