Smelly socks make the ideal mosquito trap

Scientists are working on a new mosquito trap after they discovered that mosquitoes are attracted to the odour of human smelly feet. They found that socks that had been worn for at least 10 hours were four times more attractive to mosquitoes than humans themselves.

Since mosquitoes detect humans by smell rather than sight they could not tell the difference between the socks and humans. Between 74 and 95 per cent of all those that landed on the sock traps were killed by an insecticide. The scientists involved are hoping to simplify the devices so that local villagers in Tanzania can make their own.

Mosquitoes can detect humans from up to 10m away, using carbon dioxide from the potential target’s breath. But on approaching a human they veer away from the face and towards the feet. In an experiment where African malaria mosquitoes, Anopheles gambiae, were held in a container containing additional carbon dioxide to which foot odours are added, they are unable to react to the carbon dioxide for several seconds. This could explain why mosquitoes divert towards the feet when approaching a human.

Human foot bacteria produce about 10 separate odours, some more attractive to mosquitoes than others. It is not the amount of odour that the insects find attractive, but the type of odours and the ratio between them. Determining this formula could hold the key to finding the most powerful attractant.

So the reason that some people are bitten more often than others is simply because mosquitoes prefer their smell. Of 72 types of odour receptor on mosquitoes antennae, at least 27 are tuned to detect chemicals in perspiration.