VOA慢速英语：为什么蚊子会叮你？

蚊子有种惊人的能力，能够远远地嗅到人类，然后直接飞到他们的皮肤上。遗憾的是，蚊子叮咬的后果不仅仅是痒，一些蚊子还会传播一些很严重的疾病，包括登革热、黄热和疟疾。

Mosquitoes need blood to survive and their favorite target is humans. Scientists find out why these insects prefer some people's skin more than others.

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

世界上每年有超过一百多万人民死于这些蚊子叮咬带来的疾病。一项新的研究显示了蚊子是如何选择叮咬目标的。

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

蚊子靠血液生存。它们受人类皮肤和呼吸吸引。它们能够嗅到所有哺乳动物呼出的二氧化碳气体。这种气体就是蚊子是如何察觉附近有温血动物存在的原因。

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

但是蚊子也会用它们的视觉和触觉。米歇尔·迪金森是加州理工学院的一名教授。他的一项调查显示，这些小昆虫是如何用它们更小的脑袋和三种知觉发现血液大餐的。

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

“根据我们对果蝇调查，我们怀疑视觉在蚊子找到潜在的目标寄主中很可能起很大的但不受重视的作用。”

Michael Dickinson's team used plumes – material that rises into the air -- ofcarbon dioxide gas into a wind tunnel. They then used cameras to record themosquitoes. The insects followed the plume.

迈克尔·迪金森的研究小组用一种能够飞到空中的羽毛飞进二氧化碳气体风道。他们接着用相机记录这些蚊子。蚊子跟着羽毛飞行。

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

后来，科学家们在颜色较浅的风道的地板上和墙上放置深色物体。迪金森说，刚开始，这些蚊子对这些物体一点也不感兴趣。

"What was quite striking and quite surprising is that the mosquitos fly backand forth for hours--these are hungry females--and they completely ignore theobjects 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 becomeattracted to these little visual blobs."

真正惊讶的是有蚊子来来回回地飞了几个小时，这些都是饥饿的母蚊子，它们完全忽视管道里的地板上和墙壁上的物体。但是一旦它们问到了二氧化碳的味道，它们立刻行为大变，对那些物体立马有了兴趣。

This suggested to the researchers that a mosquito’s sense of smell is moreimportant in the search for food. Once mosquitoes catch a smell of a humanor animal, they also follow visual cues.

这项研究表明，蚊子在寻找食物时嗅觉比视觉更重要。一旦蚊子问到了人类或者动物的味道，它们也会有视觉线索。

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

这真的很有意义，因为如果蚊子被它们世界中每一物体分心，它们只是在浪费时间。在这种情况下，它们一旦嗅到有可能是寄主的味道，才开始集中注意力。

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

这种情况在蚊子争斗的过程中时有发生。迈克尔·迪金森解释道，

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

我们这项实验中一些细节显示，很难长时间欺骗蚊子，它们永远会得到它们的寄主，因为在找到血液大餐前，它们会一直重复这种策略。

Matt DeGennaro is a scientist at Florida International University. He saysunderstanding a mosquito’s way of finding its host could help prevent thoseinsects from biting. He is working to create genetic changes that affect themosquito's sense of smell.

马特是佛罗里达国际大学的一名科学家。他表示，研究蚊子如何找到宿主的方式能够帮助防止被这些蚊子叮咬。他正在致力于改变影响蚊子嗅觉的基因。

"We need to know which genes control this process at all these differentstages. And then we can use that knowledge to design a new perfume thatcould block the mosquito's sensation of us or could trigger certain receptorsthat signal danger to the mosquito and then cause them to stay away."

我们需要知道在不同的阶段哪些基因控制这个过程。我们可以运用这种知识来设计一款新式香水，防止蚊子感觉到我们，或者向蚊子发出危险信号，赶它们走开。

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

这次研究发表在《现代生物》杂志上，详细的记载了蚊子的飞行，因此我们可能有一天有机会反击这些咬人的昆虫。

I’m Marsha James.

玛莎·詹姆斯为您播报。

Maia Pujara reported this story from Washington. Marsha James adapted it for Learning English. Caty Weaver was the editor.

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Words in This Story

host– n. an animal or plant in which another animal or plant lives and gets itsfood 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 airin a tall, thin shape

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

cue – 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