A spectacular wonder of nature or an anxiety-inducing nuisance? It depends on whom you ask. Naturalists have already spotted the first arrivals in a rare phenomenon during which cicadas emerge this spring across more than a dozen U.S. states — including populous areas like Chicago, Nashville and St. Louis — blanketing eastern parts of the country with billions, perhaps trillions, of the flying bugs. The insects will infiltrate a much bigger geographical area than similar occurrences in most years because they’re part of the dual emergence of two particular periodical cicada broods. These groups of multiple Magicicada species appear like clockwork after a certain number of years, but the simultaneous appearance of these two broods hasn’t happened since 1803. The Northern Illinois brood spends 17 years underground before emerging and is known as Brood XIII, while the Great Southern Brood, or Brood XIX, lives underground for 13 years. The two broods won’t coincide again until 2245. When small holes that can resemble tiny chimneys appear in the ground near tree roots, it’s a signal periodical cicadas will soon emerge from their underground lair. Once the soil hits the right temperature, around 17.8 degrees Celsius, cicada babies, called nymphs, begin to burst forth. As soon as they’re above ground, the bugs make a beeline for a vertical surface — typically a tree trunk, but it could be a fence. There they shed their hard outer skeletons and spread their wings for the first time before spending four to six weeks in a noisy frenzy of eating, mating and egg laying. The most obvious sign of their arrival is the distinctive sound they make — a droning buzz. The bugs congregate in trees, and the male cicadas form a cacophonous chorus of thousands to attract mates. “When they say it’s as loud as a lawn mower, it is as loud as a lawn mower,” said Paula Shrewsbury, a professor in the department of entomology at the University of Maryland. “We live near an airport, and when the planes are flying over…cicadas crank up their sound level, it’s like they’re competing with the airplanes for sound,” Shrewsbury said. Female cicadas use an egg-laying organ, called an ovipositor, to lay their eggs inside slits they cut into tree branches. However, cicadas are unlikely to cause any irreparable damage to plants, trees, vegetable patches or flower beds, said John Lill, a professor of biology at the George Washington University. It’s possible that the insects could damage a very young sapling, and to prevent that you could cover the sapling with protective netting, Lill said. Cicadas provide an all-you-can-eat buffet for many animals, including pets. Lill said he once had to take his dog to the vet after it gorged itself on cicadas, but the bugs — which are said to have a sweet, nutlike flavor— are not innately harmful when eaten by pets or humans. However, humans with seafood allergies should avoid eating cicadas, which are distantly related to shrimp and lobsters.(SD-Agencies) Words to Learn 相關詞匯 【滲透】 shèntòu infiltrate gradually enter, permeate, or pass through a substance or area 【產卵器】 chǎnluǎnqì ovipositor a specialized organ (as of an insect) for depositing eggs 是自然奇觀還是煩人的滋擾？這可見仁見智了。 今年春天，美國十幾個州（包括芝加哥、納什維爾和圣路易斯等人口稠密地區）將涌現一大批蟬；數十億甚至萬億只蟲蟲將出現在美國東部地區，自然學家已經注意到了首批“訪客”。 與過往大多數年份的類似情況相比，這些昆蟲今年滲透的地域范圍要大得多，因為兩種不同的周期蟬同時出現了。這些蟬每隔一些年出現，像鐘表一樣準時。自1803年以來，這兩種蟬還未同時出現過。 伊利諾斯州北部的周期蟬在地下生活了17 年后再次出現，稱為“蟬十三”，而南部的周期蟬“蟬十九”則在地下生活了13年。直到2245年，這兩種蟬才會再次同時出現。 樹根附近的地面上出現像小煙囪一樣的小洞時，周期性蟬就要從地下鉆出來了。 一旦土壤達到合適的溫度（約17.8攝氏度），稱為若蟲的蟬的幼蟲就會破土而出。離開地面，它們就直奔垂直于地面的歇腳地 —— 通常是樹干，也可能是柵欄。 在那里它們褪去硬殼，張開翅膀，然后在接下來的四到六周里瘋狂進食、交配、產卵。 宣布它們到來的最明顯標志就是蟲蟲獨特的鳴叫。為吸引配偶，成千上萬的雄蟬聚在樹上，加入聒噪的合唱。 馬里蘭大學昆蟲學系教授寶拉?什魯斯伯里說：“有人說蟬的叫聲像割草機，他們沒有夸張。” 她接著說：“我們住在機場附近，飛機飛過時 ...... 蟬還會提高音量，好像生怕自己的大合唱被飛機的轟鳴蓋過?！?/p> 雌蟬在樹枝上劃開縫隙，然后把產卵器伸進去產卵。 喬治華盛頓大學生物學教授約翰?利爾說，蟬不太可能嚴重危害樹木、菜地或花壇植物，但可能會損害幼苗。為防止這種情況，他建議給樹苗套上保護網。 蟬是許多動物的美食，包括寵物。利爾說，有一次他的狗狗吃了太多蟬，不得不去看獸醫。據說蟬有一種甜甜的堅果味；寵物或人吃了它不會有什么危害。不過，對海鮮過敏的人應該避免食用，因為它和蝦、龍蝦有很遠的親緣關系。 (Translated by Debra) | 