VOA科学技术2024--US Prepares for a Cicada Invasion Last Seen in 1803

US Prepares for a Cicada Invasion Last Seen in 1803

　　Do you remember all those cicada videos from the United States in 2021?

　　Well, prepare for a repeat performance this year. The insect show begins as early as April.

　　Two groups of cicadas, brood XIII and brood XIX, are expected to come out from the ground to mate and lay eggs this year. Their appearance in the same year is rare. The last time it happened was 1803.

　　Brood XIII is on a 17-year cycle. They will be found in the Midwestern states of Illinois, Iowa, Wisconsin and Kentucky. Brood XIX is on a 13-year cycle. They will come out in an area stretching from Indiana and Illinois southeast to the southern states of Alabama and Georgia.

　　Scientists expect more than one trillion cicadas to appear in some small areas where the two broods are close to each other. The insects will begin to climb out of the ground when the soil warms to about 18 degrees Celsius¹. So they will be seen in warmer southern areas as early as April. It will be closer to summer, sometime in June, before the cicadas arise to the north in Wisconsin, Indiana and other Midwestern states.

　　Cicadas are large, noisy insects, from about 2.5 to 5 centimeters long. Like most insects, they have wings. They also have big "bulging²" eyes. There are thousands of species of cicada around the world.

　　The huge majority of cicada species arise each year, or annually³. Then there are the periodicals which arrive after numerous years in the ground.

　　The periodical cicadas emerge to mate.

　　The male cicadas make a thrumming sound with their wings on their bodies to call for mating. The "singing" appeals to females. The insects mate and leave their fertilized⁴ eggs on trees. The resulting young fall to the ground after breaking out of their shells. They dig down into the ground where they live for years, feeding on the liquid that comes from tree roots.

　　Seven of the nine known periodical cicadas live in North America. Of the other two groups, one is in India and one is found only on the island country of Fiji.

　　Floyd Shockley is an insect scientist, or entomologist, with the Smithsonian Institution's National Museum of Natural History in Washington, D.C. He said this year's group of cicadas will include four different Magicada species within the XIX brood.

　　The next time brood XIX and brood XIII will come out in the same year will be in 2245.

　　Words in This Story

　　brood –n. a group of young (in this case insects) all born at the same time

　　thrum –v. to make a low, steady sound

　　species –n. a group of animals or plants that are similar and can produce young animals or plants

1 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

2 bulging   

膨胀； 凸出（部）； 打气； 折皱

参考例句：

• Her pockets were bulging with presents. 她的口袋里装满了礼物。
• Conscious of the bulging red folder, Nim told her,"Ask if it's important." 尼姆想到那个鼓鼓囊囊的红色文件夹便告诉她：“问问是不是重要的事。”

3 annually   

adv.一年一次，每年

参考例句：

• Many migratory birds visit this lake annually.许多候鸟每年到这个湖上作短期逗留。
• They celebrate their wedding anniversary annually.他们每年庆祝一番结婚纪念日。

4 Fertilized   

v.施肥( fertilize的过去式和过去分词 )

参考例句：

• The study of psychology has recently been widely cross-fertilized by new discoveries in genetics. 心理学研究最近从遗传学的新发现中受益匪浅。
• Flowers are often fertilized by bees as they gather nectar. 花常在蜜蜂采蜜时受粉。