2號群

2號群（Brood II），俗稱東岸群（East Coast brood），是定期於美國東北部出現的15群週期蟬之一。個體身長約4公分，成蟲活躍時間約兩週，密度高達每公頃100萬隻。每隔17年，牠們會在數週內集體羽化、聚集、產卵並死亡。^[1]

歷史

最早有關2號群的紀錄，出自美國第三任總統湯馬斯·傑弗遜在1775年的記載。他提及1724、1741、1758與1775年的2號群大發生。1775年，數以萬計的週期蟬從傑弗遜的住所蒙蒂塞洛破土而出。^[2]

2號群最後一次出現於2013年春末和夏季，預計將於2030年和2047年再次出現。^[3]

為了準確繪製2號群發生的地理範圍，全國公共廣播電台的科學節目廣播實驗室（英語：Radiolab）於2013年開啟「週期蟬追蹤者計畫」，鼓勵聽眾使用Arduino系統報告地下土壤溫度，以此預測週期蟬大發生的時間。^[4]

^ Susan L. Post. A Trill of a Lifetime. University of Illinois. 2004 [October 12, 2013]. （原始內容存檔於2012-05-11）.
^ Jefferson, Thomas. Betts, Edward Morris , 編. Thomas Jefferson's garden book, 1766-1824, with relevant extracts from his other writings. Memoirs of the American Philosophical Society (Philadelphia: American Philosophical Society (1944)). 1775, 22: 68 [2017-05-20]. LCCN 45001776. OCLC 602659598 –透過Google Books. Dr. Walker sais he remembers that the years 1724 and 1741 were great locust years. we all remember that 1758 was and now they are come again this year of 1775. it appears that they come periodically from the ground once in 17 years. they come out of the ground from a prodigious depth. it is thought they eat nothing while in this state, laying their eggs in the small twigs of trees seems to be their only business. The females make a noise well known. The males are silent.
^ Brood II. Cicada Mania. 2013-02-16 [2013-04-08]. （原始內容存檔於2010-12-23）.
^ Cicada Tracker | Radiolab. Project.wnyc.org. [2013-04-08]. （原始內容存檔於2021-01-22）.
^ Citizen Science: Cicada Watch. 17 April 2013 [24 April 2013]. （原始內容存檔於2013-06-18）.