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The guest you don't want on the patio, mosquitoes

Mosquitoes find you three ways. Here's how, new study finds

Leeanna McLean
Digital Reporter

Saturday, July 18, 2015, 8:48 PM - You may want to hold your breath the next time you are surrounded by mosquitoes.

A new study published in the journal Current Biology shows the bloodthirsty insects are attracted by three things: smell, sight and heat.

The Weather Network’s recent bug outlook shows this summer will be worse than usual for mosquitoes in many areas of the country and unfortunately, research illustrates it isn’t easy to shoo away the pesky insects.

Scientists from the California Institute of Technology and the University of Washington were able to examine the movement of mosquitoes inside a wind tunnel by using cameras and 3D tracking software.

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The three different stimuli were represented in the study by a plume of CO2, a black spot on the floor of the tunnel and heated glass containers.

Results show the insects are able to first detect suitable hosts by the presence of a plume of CO2, such as when humans exhale. They track by surging upwind and casting crosswind, the study notes.

Once the researchers confirmed how mosquitoes use smell to locate a host, thermal sensors were examined.

“In a previous experiment with fruit flies, we found that exposure to an attractive odor led the animals to be more attracted to visual features,” Floris van Breugel, author of the study told the Medical Daily. “This was a new finding for flies, and we suspected that mosquitoes would exhibit a similar behavior.”

Mosquito emerging from its nymph stage. Photo by Paul Turton, Wainfleet, Ont., July 15, 2014

All three cues work together to play a vital role in target formation. For example, if the insects were presented with a black spot but there was no CO2 plume, they left the heated glass containers alone. However, if the CO2 plume was there, they would sniff it out and head towards the visual stimulus.

Researchers then developed a model to show how mosquitoes locate a host from different distances. At 10 to 50 metres, mosquitoes use smell to sense CO2. If the mosquito is stimulated by scent, at five to 15 metres, they will head towards something visually interesting. Finally, once within one metre the insects zero in on body heat.

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While holding your breath may seem like a good idea, the researchers say it isn’t enough.

“Even if it were possible to hold one’s breath indefinitely, another human breathing nearby, or several metres upwind, would create a carbon dioxide plume that could lead mosquitoes close enough to you that they may lock on to your visual signature,” the study notes.

Scientists believe the strongest defense is to become invisible or at least visually camouflaged. However, mosquitoes can still track body heat.

Therefore, the study concludes it’s very difficult to escape the blood suckers and the host seeking strategy is “annoyingly robust.”

While most Canadians try almost anything to rid themselves of mosquitoes, Russians celebrate the irritating insect. The three-day 2015 Russian Mosquito Festival kicked off on Friday.

Sources: BBC | Medical Daily | Study

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