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，北美东半部变成了一个巨大的痰盂，“吐口水”的是一群叫做吹沫虫的昆虫。随便走在一片草坪上，你都能看到它们凝结成块的"唾沫“粘在各种植物的茎部。吹沫虫怎么会分泌出如此多的"唾液"？

 

　　随着春天来临，天气转暖，吹沫虫在秋天产下的虫卵开始孵化。吹沫虫幼虫用针状口器刺破植物茎部，吸取汁液。但它们吸取的不是光合作用的“产品”- 营养丰富的含糖汁液，而是光合作用的“原料”- 植物根部从土壤里汲取的水分和其它元素。

 

　　为了从“兑水”的汁液中汲取养分，吹沫虫每24小时需要吸食高达自身重量300倍的植物汁液。你看到的植物茎部上的“唾沫”正是他们排出的多余水分。

 

　　成块的唾沫给人的第一感觉无外乎大堆无用的唾液，其实它还能保护吹沫虫幼虫免遭捕食。这个“隐身”的功效如此甚好，至今人类还未发现吹沫虫的捕食者。"唾 沫"还能为吹沫虫提供了湿润的环境，让它们没有干涸之虞。但是彼之蜜糖，吾之毒药。植物却可能随着根部汁液被夺食而发育不良，甚至枯萎。