英語聽力文摘559 世界上比較大的痰盂！
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- 參考譯文
In the spring, the eastern half of North America turns into one big spittoon for spittlebugs. Wandering through a meadow, it’s easy to spot the gobs of foam they produce, stuck to the stems of various plants. What makes spittlebugs produce so much spittle?
As the weather warms in spring, spittlebug eggs that were laid on plants in autumn begin to hatch. The spittlebugnymphs pierce the plant stem with their needle-like mouth parts and suck sap from the plant. But, the nymphs don’t suck the nutrient-rich sap that carries sugars produced by photosynthesis. Instead, they pump out the sap that flows up from the roots, carrying water and other elements from the soil necessary for photosynthesis.
To get enough nutrients from this watery sap, spittlebugs have to pump up to 300 times their own weight in sap every 24 hours! They excrete the excess water in the form of that spittle you see on the plant stem.
The frothy mass may seem at first to be so much wasted spittle, but it also serves an important function by protecting and concealing the nymphs from predators. It works so well that the critters have no known predators. The spittle also provides a moist environment for the nymphs, preventing them from drying up. That’s good news for spittlebugs but bad news for plants, which can wilt and become stunted as the nymphs pump out the sap flowing up from their roots.
世界上最大的痰盂!
春天，北美東半部變成了一個巨大的痰盂，“吐口水”的是一群叫做吹沫蟲的昆蟲。隨便走在一片草坪上，你都能看到它們凝結成塊的"唾沫“粘在各種植物的莖部。吹沫蟲怎么會分泌出如此多的"唾液"?
隨著春天來臨，天氣轉暖，吹沫蟲在秋天產下的蟲卵開始孵化。吹沫蟲幼蟲用針狀口器刺破植物莖部，吸取汁液。但它們吸取的不是光合作用的“產品”- 營養(yǎng)豐富的含糖汁液，而是光合作用的“原料”- 植物根部從土壤里汲取的水分和其它元素。
為了從“兌水”的汁液中汲取養(yǎng)分，吹沫蟲每24小時需要吸食高達自身重量300倍的植物汁液。你看到的植物莖部上的“唾沫”正是他們排出的多余水分。
成塊的唾沫給人的第一感覺無外乎大堆無用的唾液，其實它還能保護吹沫蟲幼蟲免遭捕食。這個“隱身”的功效如此甚好，至今人類還未發(fā)現吹沫蟲的捕食者。"唾 沫"還能為吹沫蟲提供了濕潤的環(huán)境，讓它們沒有干涸之虞。但是彼之蜜糖，吾之毒藥。植物卻可能隨著根部汁液被奪食而發(fā)育不良，甚至枯萎。
