Mosquitoes smell before they eat

Biologists have discovered that mosquitoes use their sense of smell to find food.

A research team at the University of Washington used odour stimulus and discovered that mosquitos employ a sharp sense of smell to detect suitable hosts by the presence of CO₂.

In the study, published in Current Biology, the team used wind tunnels – mostly featureless, with the exception of a small dark dot on the floor – to track and record the behaviour of mosquitoes.

“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. We can really test different cues and the mosquito's response to them,” said Professor Jeff Riffell at the University of Washington.

The team released CO₂ – gas that people exhale with each breath – into the tunnel and discovered that when mosquitoes were exposed to odour, they were attracted to the black dot. They suggest the reason for the attraction is due to the assumption a warm-blooded host is near-by.

The scientists believe that the olfactory bulb – the part of brain involved in the sense of smell – may control these insects’ sensory systems.

Professor Riffell said: “When we gave them the odour stimulus, all of the sudden they were attracted to this black dot. It's almost like the carbon dioxide gas turned on the visual stimulus for the mosquitoes to go to this black dot.”

After releasing CO₂ in the tunnel, the biologists added water vapour in the tunnel and found that the mosquitoes’ affinity for the dot increased.

“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. And then they start using vision and other body odours 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,” added Professor Riffell.

The team hope these findings will help them understand how insects integrate and interpret different signals from their environment and use this information to make decisions.

“What our research shows is that it's not one kind of odour or stimulus that's attracting mosquitoes; it's a real combination of cues,” Said Professor Riffell.

Next, the scientists plan to study how other scents might affect mosquito behaviour.

Paper: http://www.cell.com/current-biology/abstract/S0960-9822(15)00740-X