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This Scientific Americans 60 senconds science. I'm Cythia Graber. This will just take a minute.

How did the zebra get stripes. One theory holds that stripes help confused predators¹. But stripes might be primarilly to protect zebras from ferocious² insects. That's according to the study in the Journal of Experimental Biology. Horseflys are abundant in Africa, they deliver a painful bite that's spread diseases and destruct animals from grazing, the flies use polarized light hiding water as a guide to place to mate and lay leggs. And they readlike such light hiding dark in mamal hairs as sign of blood meal. Zebra embryos³ start out dark and developed their white stripes before birth. Could the stripes confuse flies?

The researchers just went to a farm infested⁴ with horse flies ,where they set up models a black and white stripes of varying angels and widths. That's changing the direction of their reflected polarized eyes light. They tracked at the patterns that the flies are interested. They then tested the models of horse's colour, black, brown, white or zebra's striped. and again tracted the effect on flies. Turns out that black and white stripes on zebra are optimal⁵ for avoiding of horseflies attention.Meaning that zebra may evolve stripes to ward⁶ off the disease-carrying insects and to dine in peace.

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1 predators
n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）
参考例句：
birds and their earthbound predators 鸟和地面上捕食它们的动物 The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。来自《简明英汉词典》

2 ferocious
adj.凶猛的，残暴的，极度的，十分强烈的
参考例句：
The ferocious winds seemed about to tear the ship to pieces.狂风仿佛要把船撕成碎片似的。 The ferocious panther is chasing a rabbit.那只凶猛的豹子正追赶一只兔子。

3 embryos
n.晶胚；胚，胚胎( embryo的名词复数 )
参考例句：
Somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段，而且其行为象胚。来自辞典例句 Evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。来自辞典例句

4 infested
adj.为患的，大批滋生的（常与with搭配）v.害虫、野兽大批出没于( infest的过去式和过去分词 )；遍布于
参考例句：
The kitchen was infested with ants. 厨房里到处是蚂蚁。 The apartments were infested with rats and roaches. 公寓里面到处都是老鼠和蟑螂。

5 optimal
adj.最适宜的；最理想的；最令人满意的
参考例句：
What is the optimal mix of private and public property rights in natural resources?私人和国家的自然资源产权的最适宜的组合是什么？ Optimal path planning is a key link for the sailing contest.帆船最优行驶路径规划是帆船比赛取胜的关键环节。

6 ward
n.守卫，监护，病房，行政区，由监护人或法院保护的人（尤指儿童）；vt.守护，躲开
参考例句：
The hospital has a medical ward and a surgical ward.这家医院有内科病房和外科病房。 During the evening picnic,I'll carry a torch to ward off the bugs.傍晚野餐时，我要点根火把，抵挡蚊虫。