为什么打苍蝇这么难?
Why are flies so hard to swat?
864字
2021-01-14 21:46
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火星译客

The house fly is known for its evasive maneuvers.

家蝇以其回避动作而闻名。

(Image: © Suman Acharya/Alamy Stock Photo)

图片:©Suman Acharya / Alamy Stock Photo)

A fly buzzes past your head and lands nearby; you snatch a flyswatter or roll up a magazine and approach cautiously — and you strike! 

一只苍蝇嗡嗡飞过你的头顶,落在附近;你抓起一把苍蝇拍,或者卷起一本杂志,小心翼翼地靠近——然后你就下手了!

But no matter how quick you are, the fly is almost always faster, and it usually manages to evade your wallop and escape unharmed. (Is it trying to annoy you?!)

但无论你跑得多快,苍蝇总是比你快,而且它通常会设法躲开你的打击,毫发无损地逃脱。(它是不是想惹恼你?!)

Flies have many adaptations that lend them heightened speed, maneuverability and perception, making them very, very good at detecting and evading even the swiftest swats. And new evidence shows that flies' modified hind wings play an important part in launching them into a speedy takeoff — often just in the nick of time.

苍蝇有很多适应性,这些适应性使它们的速度、机动性和感知能力都得到了提高,使它们非常非常擅长侦测和躲避速度最快的猛击。新的证据表明,苍蝇改良的后翅在使它们快速起飞中起着重要作用——通常是在关键时刻。

House flies (Musca domestica) belong to the order Diptera, or true flies. Diptera flies possess modified hind wings that have evolved into sticklike structures with a knob at the end, called halteres. Their vibrations help the insects stabilize their bodies while in flight, by sensing body rotations and transmitting information to the wings.   

家蝇属于双翅目,或真蝇。双翅目蝇的后翅经过改良,进化成末端有旋钮的棍状结构,称为笼头。它们的振动通过感知身体的旋转并将信息传递给翅膀,从而帮助昆虫在飞行中稳定身体。

Flies in the Diptera subgroup Calyptratae, which includes house flies, also vibrate their halteres while walking, but scientists didn't know why. In a study published online Jan. 13, 2021 in the journal Proceedings of the Royal Society B: Biological Sciences, researchers investigated Calyptratae flies to see if haltere oscillation affected their transition into the air, directing additional sensory input to help coordinate movements in the wing and leg muscles.  

双翅目有瓣蝇亚群(包括家蝇)中的苍蝇在走路时也会抖动它们的笼头,但科学家不知道为什么。在2021年1月13日在线发表在《英国皇家学会学报B:生物科学》杂志上的一项研究中,研究人员调查了有瓣蝇类,看它们的颈圈摆动是否会影响它们向空气的过渡,从而引导额外的感官输入来帮助协调翅膀和腿部肌肉的运动。

Using high-speed cameras to capture tethered and free laboratory-reared flies during takeoff, the scientists recorded footage at speeds up to 3,000 frames per second. They found that Calyptratae flies launched themselves around five times faster than other flies; their takeoffs required an average of about 0.007 seconds (7 milliseconds) and just one wingbeat. 

在起飞过程中,科学家们使用高速摄像机捕捉拴在实验室和自由饲养的苍蝇,以每秒3000帧的速度记录下来。他们发现有瓣蝇的飞行速度是其他蝇类的5倍;它们的起飞平均需要约0.007秒(7毫秒)和一次翼拍。

"None of the Calyptratae had a takeoff duration longer than 14 milliseconds [0.014 seconds]," the researchers reported. By comparison, non-Calyptratae flies' takeoffs lasted about 0.039 seconds (39 milliseconds) and required about four wingbeats, according to the study. 

研究人员报告说:“没有一种有瓣蝇类的起飞时间超过14毫秒(0.014秒)。”相比之下,非有瓣蝇类的起飞只持续了0.039秒(39毫秒),需要四次翼拍。

Next, the researchers removed the halteres, which all Diptera flies have. Calyptratae flies lacking these knobby structures took a lot longer to become airborne, but takeoff time wasn't affected in non-Calyptratae flies without halteres. Stability during takeoff also suffered with haltere removal, but only in Calyptratae flies. For example, the Calyptratae insects known as blow flies that attempted escape takeoffs without their halteres "always resulted in a crash landing," the scientists reported.

接下来,研究人员去掉了所有双翅目果蝇的笼头。没有这些节状结构的有瓣蝇类需要更长的时间进入空中,而没有笼头的非有瓣蝇类起飞时间不受影响。除去笼头也会影响起飞时的稳定性,但仅限于有瓣蝇类。例如,科学家们报告说,被称为“吹蝇”的有瓣蝇类昆虫试图不戴笼头逃离起飞,“总是导致紧急着陆”。

"Haltere use thus allows for greater speed and stability during fast escapes — but only in the Calyptratae clade," the scientists wrote in the study. 

科学家们在研究中写道:“因此,使用缰绳可以在快速逃脱时获得更大的速度和稳定性——但这仅限于有瓣蝇类。”

In the blink of an eye

一眨眼的功夫

Halteres aren't the only secret weapon in a fly's evasive arsenal; once a fly is airborne, it can execute maneuvers that would be the envy of a fighter jet pilot. Fruit flies can change course in under 1/100th of a second — about 50 times faster than an eye can blink, Live Science previously reported. In experiments, perfectly timed wing flaps generated enough force to rapidly propel the flies away from a predator while in mid-air. 

笼头并不是苍蝇躲避武器库中唯一的秘密武器;一旦苍蝇在空中飞行,它可以执行一些让战斗机飞行员羡慕不已的动作。据《生活科学》杂志此前报道,果蝇可以在不到百分之一秒的时间内改变路线,比眼睛眨眼的速度快50倍。在实验中,完美时机的拍打翅膀会产生足够的力量,使苍蝇在半空中迅速远离捕食者。

"These flies roll up to 90 degrees — some are almost upside down — to maximize their force, and escape," Florian Muijres, who studied the biomechanics of flight at the University of Washington in Seattle, and is now at Wageningen University & Research in the Netherlands, told Live Science in 2014. 

“为了最大限度地发挥力量,这些苍蝇会向上卷起90度,有些甚至是上下颠倒,”西雅图华盛顿大学(University of Washington)研究飞行生物力学的弗洛里安·缪伊雷斯(Florian Muijres)在2014年接受《生活科学》(Live Science)采访时表示。

Flies also have exceptional vision, which helps them plan their jumps away from a threat. About 200 milliseconds before takeoff, fruit flies use visual input warning of looming danger to adjust their posture and pinpoint the direction that will launch them to safety, scientists wrote in 2008 in the journal Current Biology

苍蝇也有特殊的视力,这有助于它们计划跳跃以避开威胁。科学家在2008年发表在《当代生物学》杂志上的一篇文章中写道,在起飞前约200毫秒,果蝇使用视觉输入的危险警告来调整它们的姿势,并确定将它们发射到安全地带的方向。

In fact, their enhanced perception juggles up to six times more visual input in one second than humans can, the BBC reported in 2017.

英国广播公司2017年报道称,事实上,它们在一秒钟内处理视觉输入的能力是人类的6倍。

Animal brains perceive the passage of time by processing images at speeds known as the "flicker fusion rate," a term describing how many images flash into their brains per second. Roger Hardie, a professor emeritus of cellular neuroscience at the University of Cambridge in England, implanted electrodes into the photoreceptors of flies' eyes to measure their flicker fusion rate, calculating it to be 400 times per second; the average flicker fusion rate for humans is about 60, according to the BBC. This means that movement you perceive as "normal" moves like slow-motion to a fly.

动物的大脑通过处理图像的速度来感知时间的流逝,这种速度被称为“闪烁融合速度”,这个术语描述了每秒有多少图像闪现到它们的大脑中。罗杰·哈迪(Roger Hardie)是英国剑桥大学(University of Cambridge)细胞神经科学的荣誉退休教授,他将电极植入苍蝇眼睛的光感受器,以测量它们的闪烁融合率,计算出其为每秒400次;据BBC报道,人类的平均闪烁融合率约为60。这意味着你认为“正常”的动作对苍蝇来说就像慢动作。

With all these built-in advantages, it's no wonder that the fly you're trying to swat can escape. However, one approach that might improve your chances is aiming your swat at a spot where the fly is likely to go, rather than where it's resting, Michael Dickinson of the California Institute of Technology in Pasadena told The Independent in 2011.

有了所有这些内在的优势,难怪你试图拍打的苍蝇能逃脱。然而,帕萨迪纳市加州理工学院的迈克尔·迪金森(Michael Dickinson)在2011年告诉《独立报》(the Independent),有一种方法可能会提高你拍苍蝇的几率,那就是瞄准苍蝇可能会飞到的地方,而不是它休息的地方。

"It is best not to swat the fly's starting position," Dickinson said. "Aim a bit forward of that to anticipate where the fly is going to jump."

“最好不要拍打苍蝇的起始位置,”Dickinson说。“把目标再向前一点,以便预测苍蝇会往哪里跳。”

Originally published on Live Science.

最初发表在《生命科学》上。

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