February 03, 2019

How do mosquitoes find us? Thinking like a mosquito.

How do mosquitoes find us? Thinking like a mosquito.

Have you ever wondered how mosquitoes know exactly where we are?

Why do we always have that one mosquito-magnet friend in our group who gets bitten first or bitten more, despite wearing the exact amount of clothes?

What does a female mosquito look out for when she is looking for her next blood meal?

The answers here will help you think like a female mosquito.

 Mosquitoes do not have sensory organs like us humans to pick up on shapes, colours and sound the way we do. Instead, mosquitoes rely on these three cues to detect an animal to feed on for blood:

  1. Carbon dioxide (CO2)
  2. Heat
  3. Lactic acid

A female mosquito relies on blood meal for protein to produce eggs. Her source of blood meal usually comes from mammals (like us humans) and other vertebrates (from birds to even frogs).

These animals inhale oxygen, and guess what is exhaled? Carbon dioxide!

When female mosquitoes are on lookout for blood meal, their sensors responsible in detecting carbon dioxide will point them in direction of higher carbon dioxide concentration. It only takes a single (breathing) person or animal to emit more carbon dioxide than its surroundings to create a decentplume of signal for female mosquitoes to fly to.

Imagine a group of friends going for a jog at MacRitchie Reservoir in a sunny humid afternoon!

Heat-seeking mode turns on.

Once female mosquitoes get closer to the source of carbon dioxide, their heat sensors will then be used to zero in. Using heat helps the mosquitoes to separate us in the cloud of carbon dioxide that we emit,from trees and other objects that do not product heat. Imagine it like the Predator’s thermal vision in the 1987 movie Predator, starring Arnold Schwarzenegger.

The cocktail of attractants is up next.

Next, the third cue is usually what separates a mosquito-magnet person from his/her friends in a group. Lactic acid is a component in our body’s metabolism and can be found on our skin, and our breath too. Some people have higher concentration of it, while some people have lower concentration, even when both groups are in same relaxed state.

When we exercise or perform more robust activity especially in warm and humid environment, it causes intense sweating and increased breathing. Those two processes releasemore lactic acid from our body than when we are less sweaty and breathing slowly.

Can we control the amount of carbon dioxide, heat and lactic acid we emit to the mosquitoes?

The concentration of cues we give out to mosquitoes are mostly determined by genetics and physiology. No amount of Vitamin B pill-popping, nor garlic-chewing can significantly alter the way mosquitoes target us.

The good news is that we can still enjoy being outdoors in the nature and avoidbites from mosquitoes at the same time.All we need to do is to pay attention to our choice of repellents and how we use them. Other than that, we can put on longer clothing such as long sleeves and long pants to cover up more skinto avoid giving the mosquitoes the access to bite us.


© Jo-Lynn Teh, BCE

 Jo-Lynn Teh is ESA Board Certified Entomologist based in Singapore. While her specialisation is on tropical insects that affect public health and agriculture, Jo-Lynn’s passion is also to help people understand insects. Find her on LinkedIn.

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