【英语时差8,16】会发射紫外线的蜘蛛（上）

Many spiders make their webs attractive to insects by using special silks that reflect ultraviolet light, according to a study by two scientists working at Yale University. Ultraviolet light is the component¹ of sunlight that causes suntans and sunburns. We can’t see ultraviolet light, but insects can. Ultraviolet light seems to provide at least two important signals to insects. First, it signifies open space, because the only natural sources of ultraviolet light are the sun and the sky. Second, ultraviolet-reflecting bars, crosses, circles, and other patterns on flowers serve as targets that attract pollinating insects. The authors of the study, Catherine Craig and Gary Bernard, found that many spiders make webs entirely² of silk that reflects ultraviolet light. Apparently³ these webs attract insects because the webs look like patches of open sky to insect eyes.

1 component   

n.组成部分，成分，元件；adj.组成的，合成的

参考例句：

• Each component is carefully checked before assembly.每个零件在装配前都经过仔细检查。
• Blade and handle are the component parts of a knife.刀身和刀柄是一把刀的组成部分。

2 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

3 apparently   

adv.显然地；表面上，似乎

参考例句：

• An apparently blind alley leads suddenly into an open space.山穷水尽，豁然开朗。
• He was apparently much surprised at the news.他对那个消息显然感到十分惊异。