为什么蚊子会叮你?

Why Do Mosquitoes Choose to Bite You? 为什么蚊子会叮你?

Mosquitoes have an extraordinary ability to target humans far away and fly straight to their unprotected skin. Regrettably, mosquitoes can do more than cause an itchy wound. Some mosquitoes spread several serious diseases, including Dengue, yellow fever and malaria¹.

Over one million people worldwide die from these mosquito-borne diseases each year. New research now shows how mosquitos choose who to bite.

Mosquitoes need blood to survive. They are attracted to human skin and breath. They smell the carbon dioxide gas -- which all mammals breathe out.  This gas is how mosquitoes know that a warm-blooded creature is nearby.

But mosquitoes also use their eyes and sense of touch. Michael Dickinson is a professor at the California Institute of Technology. His research shows how these small insects, with even smaller brains, use three senses to find a blood meal. 

"We suspected from research that we had been doing on fruit flies that vision might play a very large and underappreciated role in allowing the mosquito to really home in on the potential host target."

Michael Dickinson's team used plumes³ – material that rises into the air -- of carbon dioxide gas into a wind tunnel. They then used cameras to record the mosquitoes. The insects followed the plume².

Then, the scientists placed dark objects on the lighter⁴ colored floor and walls of the tunnel. Mr. Dickinson said, at first, the mosquitoes showed no interest in the objects at all.

"What was quite striking⁵ and quite surprising is that the mosquitos fly back and forth⁶ for hours--these are hungry females--and they completely ignore the objects on the floor and wall of the tunnel. But the moment that they get a hit of CO2, they change their behavior quite dramatically and now would become attracted to these little visual blobs."

This suggested to the researchers that a mosquito’s sense of smell is more important in the search for food. Once mosquitoes catch a smell of a human or animal, they also follow visual cues⁸.

"This really makes a lot of sense because if the mosquitoes were distracted⁹ by every visual object in their world, they would just waste all their time. This case, they only start paying attention when their nose tells them that there might be a host nearby."

This process happens several times over the course of a mosquito's flight. Michael Dickinson explains.

"What some of the details of our experiments indicated is that it's very hard to fool them over the long run. They will always get their man or woman over time because they'll just keep repeating this strategy until they find a yummy meal. "

Matt DeGennaro is a scientist at Florida International University.  He says understanding a mosquito’s way of finding its host could help prevent those insects from biting. He is working to create genetic¹⁰ changes that affect the mosquito's sense of smell.

"We need to know which genes¹¹ control this process at all these different stages. And then we can use that knowledge to design a new perfume that could block the mosquito's sensation¹² of us or could trigger¹³ certain receptors that signal danger to the mosquito and then cause them to stay away."

The study, published in Current Biology, details the steps of the mosquito's flight so that we may one day have a fighting chance against the biting insect.

Words in This Story

host – n. an animal or plant in which another animal or plant lives and gets its food or protection

underappreciated – adj. not given the respect or thanks that is deserved

plume – n. something (such as smoke, steam, or water) that rises into the air in a tall, thin shape

blob – n. something that does not have a regular shape

cue⁷ – n. something that suggests the nature of what is being seen, smelled,  heard etc.

yummy – adj. very pleasing to the taste

trigger – v. to cause something to start or happen

receptor – n. a nerve ending that senses changes in light, temperature, pressure, and causes the body to react in a particular way

1 malaria   

n.疟疾

参考例句：

• He had frequent attacks of malaria.他常患疟疾。
• Malaria is a kind of serious malady.疟疾是一种严重的疾病。

2 plume   

n.羽毛；v.整理羽毛，骚首弄姿，用羽毛装饰

参考例句：

• Her hat was adorned with a plume.她帽子上饰着羽毛。
• He does not plume himself on these achievements.他并不因这些成就而自夸。

3 plumes   

羽毛( plume的名词复数 )； 羽毛饰； 羽毛状物； 升上空中的羽状物

参考例句：

• The dancer wore a headdress of pink ostrich plumes. 那位舞蹈演员戴着粉色鸵鸟毛制作的头饰。
• The plumes on her bonnet barely moved as she nodded. 她点点头，那帽子的羽毛在一个劲儿颤动。

4 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。

5 striking   

adj.显著的，惹人注目的，容貌出众的

参考例句：

• There is a striking difference between Jane and Mary.简和玛丽之间有显著的差异。
• What is immediately striking is how resourceful the children are.最令人注目的是孩子们的机智聪明。

6 forth   

adv.向前；向外，往外

参考例句：

• The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
• He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。

7 cue   

n.暗示，信号，提示；vt.提示，暗示

参考例句：

• When she coughs,it's my cue to come onto the stage.她一咳嗽，就是给我暗号出场。
• The actor missed his cue and came onto the stage late.这演员错过了向他发出的提示，上场晚了。

8 cues   

n.尾白( cue的名词复数 )；提示；暗示；（台球等的）球杆v.向…发出指示信号( cue的第三人称单数 )

参考例句：

• Without him they forgot their cues and garbled their lines. 一旦没有了他，她们就忘掉了她们的结尾语，或者弄错了台词。 来自辞典例句
• She does not tiptoe through life taking cues from others. 她从来不依葫芦画瓢小心翼翼地生活。 来自互联网

9 distracted   

a.注意力分散的，思想不集中的

参考例句：

• When working, one should concentrate and not allow oneself to be distracted. 工作时要集中精力，不要分心。
• Noise outside distracted her mind from her studies. 门外的噪音使她心神不宁，无法集中注意力学习。

10 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

11 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

12 sensation   

n.感觉，感知力，激动，轰动

参考例句：

• He lost all sensation in his legs through cramp.他的腿部因抽筋而失去知觉。
• Seeing him again after so many years was a strange sensation.那么多年以后又见到他，是一种不可思议的感觉。

13 trigger   

n.触发器，板机，制滑机；v.触发（事件）

参考例句：

• His index finger tightened on the trigger but then relaxed again.他的食指扣住扳机，然后又松开了。
• He pulled the trigger but the gun didn't go off.他打了一枪，没有发火。