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Mosquitoes smell their meals before they see them

"Carbon dioxide is the best signal for a warm-blooded animal, and they can sense that from up to 30 feet away," explained researcher Jeff Riffell.

By Brooks Hays
Mosquito bites skin, sucks blood. Researchers suggest the feeding process is aided by the insect's sense of smell. Photo by UPI/Shutterstock/Kitsadakron_Photography
Mosquito bites skin, sucks blood. Researchers suggest the feeding process is aided by the insect's sense of smell. Photo by UPI/Shutterstock/Kitsadakron_Photography

SEATTLE, July 16 (UPI) -- Before mosquitoes set their eyes on a fresh meal of blood, their sense of smell rings the dinner bell and guides them to the table.

It's taken a long time for scientists to figure out exactly how bloodsuckers like mosquitoes go about seeking out a ripe host. But new research suggests the insect's sense of smell plays a vital role in securing regular meals.

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Researchers were able to track mosquito behavior under a variety of circumstances by watching them in a wind tunnel, a closed and controlled environment.

"What's great about this wind tunnel is that it provided a nice control of wind conditions and the environment these mosquitoes are flying around in," Jeff Riffell, a biologist at the University of Washington and co-author of a new paper on mosquitoes' sense of smell, said in a press release. "We can really test different cues and the mosquito's response to them."

As Riffell explains, the wind tunnel experiment actually featured few variables and few stimuli. The unadorned wind tunnel features only a single black dot on the floor. Under regular conditions, the mosquitoes were uninterested in the dot. But when bursts of CO2 were released into the chamber -- mimicking the breath of an animal -- the mosquitoes suddenly became interested in the dot, choosing to make their way to it and land upon it.

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The unique behavior suggests mosquitoes gate their sensory responses. Once their smell clues them into the possible presence of a living blood-filled creature, the insects' other senses take over, guiding them to a potential host.

"Carbon dioxide is the best signal for a warm-blooded animal, and they can sense that from up to 30 feet away -- quite a distance," explained Riffell. "And then they start using vision and other body odors to discriminate whether we're a dog or a deer or a cow or a human. That may be how they discriminate among potential blood hosts."

Riffell and his colleagues are now testing how mosquito brains react to different smells, in order to better understand what bodily odors are most important in triggering feeding.

"A lot of papers have been trying to find these odor sources that could repel or attract mosquitoes," said Riffell. "What our research shows is that it's not one kind of odor or stimulus that's attracting mosquitoes, it's a real combination of cues."

The new research is published in the journal Current Biology.

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