Shades of Blue Stop a Mosquito Biting You

Blues and Greens are in this Summer…
01 March 2022

MOSQUITO_ON_SKIN

Female Aedes albopictus mosquito on skin

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Mosquitoes transmit a series of diseases such as zika and malaria by biting humans. So how do we keep them away? Colour and CO2 seem to be important factors in all of this.

Mosquitoes have a direct connection between their olfactory system and photoreceptors. Photoreceptors are types of cells that are able to respond to light and possibly also distinguish colours of light. Just as we are able to see colour by eye, mosquitoes can too. But the difference here is that this is activated by the olfactory system. Mosquitoes are sensitive to CO2, temperature, and sweat which all influence their attractiveness to humans. CO2 is an understudied factor of these and the inhalation of it by mosquitoes, results in them being visually sensitised. This means that they are able to look for us and specifically colours reflected from our skin. Human skin emits colours on the redder end of the electromagnetic spectrum which seems to be the colours mosquitoes are attracted to. But what about if we emitted colours on the bluer end of the spectrum? And are some colours more attractive to mosquitoes than others? Professor Jeff Riffell from the University of Washington and his colleagues looked at the attractiveness of different colours towards mosquitoes.

A wind tunnel was set up to mimic the environment mosquitoes reside in and the mosquitoes were released inside it. Differently coloured objects were placed inside this wind tunnel and the mosquitoes primarily were attracted to the red or orange objects, avoiding the blues and greens. Though the red wavelength is close to the infrared this attractiveness doesn't spill over to the IR. The mosquitos can’t detect the IR by eye. They do however have temperature sensors on their antennae which can detect heat and hence are again attracted to human skin.

Could we genetically modify these mosquitoes to stop them from biting us and would that impact our ecosystem? Riffell says “They had tested genetically modified mosquitoes which were blind to us”, i.e their photoreceptors were knocked out, and therefore “their visual attraction to us was eliminated.” It’s too early to decipher whether these impact our ecosystem but it is a step forward to preventing zika and malaria spreading.

Knowing that mosquitoes are attracted to reds and oranges, what can we do to avoid getting bitten? Blue and green coloured clothing works well as well as not talking too much…

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