WEBVTT - Why Do 17-Year Cicadas Appear Almost Every Year? 0:00:01.920 --> 0:00:06.360 Welcome to brain Stuff, a production of iHeart Radio, Hey 0:00:06.360 --> 0:00:09.879 brain Stuff Lawn bold bomb here in May or April 0:00:09.960 --> 0:00:12.920 of this year. One of the largest broods of seventeen 0:00:13.000 --> 0:00:16.480 year Cicadas brewed ten written with the Roman numeral X, 0:00:16.840 --> 0:00:19.959 is going to emerge from its underground layers across the 0:00:19.960 --> 0:00:23.080 eastern United States, from New York down to Georgia and 0:00:23.120 --> 0:00:28.080 west out to Illinois. These are periodical cicadas, insects measuring 0:00:28.120 --> 0:00:30.720 about one and a half inches or four centimeters in length, 0:00:30.880 --> 0:00:34.400 with a red orange hue and protruding red eyes. This 0:00:34.560 --> 0:00:38.000 coloring is an easy way to identify periodical cicadas from 0:00:38.000 --> 0:00:42.000 other species, including the more common dog day cicadas, which 0:00:42.040 --> 0:00:44.280 appear every year at the end of summer and have 0:00:44.520 --> 0:00:49.920 green tinged wings. Periodical cicadas make a rare appearance, relegated 0:00:49.960 --> 0:00:53.280 only to the regions east of the United States Great Plains, 0:00:53.520 --> 0:00:57.200 and nowhere else in the world. In eighteen nine, three 0:00:57.280 --> 0:01:02.280 observers began organizing periodical cicada as into broods. This makes 0:01:02.320 --> 0:01:06.720 it easier to track the insects infrequent arrivals. Each brood 0:01:06.760 --> 0:01:09.800 includes different species of cicadas that emerge together in a 0:01:09.840 --> 0:01:13.480 collective and noisy bid to find suitable mates. There are 0:01:13.520 --> 0:01:16.520 twelve broods of seventeen year cicadas and three broods of 0:01:16.560 --> 0:01:19.760 thirteen year cicadas, which are more prevalent in the southeastern 0:01:19.800 --> 0:01:23.120 part of the United States. Each brood operates on a 0:01:23.120 --> 0:01:25.920 different schedule, which means you don't have to wait thirteen 0:01:26.040 --> 0:01:29.760 or seventeen years to witness the insects next in mass eruption. 0:01:30.319 --> 0:01:33.480 After this year's brewed ten appearance, will get broods thirteen 0:01:33.520 --> 0:01:40.360 and nineteen four and brewed fourteen in. The sudden appearance 0:01:40.400 --> 0:01:44.160 of seventeen year cicadas is one of nature's most spectacular events, 0:01:44.200 --> 0:01:47.120 a phenomenon that perhaps led to the fanciful naming of 0:01:47.200 --> 0:01:53.400 the periodical cicadas genus classification magic Cicada. For centuries, periodical 0:01:53.440 --> 0:01:58.320 cicadas have fascinated scientists and casual observers alike. Millions of 0:01:58.320 --> 0:02:01.640 cicadas may emerge in a single night after spending seventeen 0:02:01.720 --> 0:02:05.520 or thirteen years living underground, feeding off of nutrients sucked 0:02:05.520 --> 0:02:08.480 from the roots of trees and other plants. It's this 0:02:08.639 --> 0:02:12.160 lengthy childhood that serves as an important distinction that enables 0:02:12.200 --> 0:02:14.720 them to have the longest lifespan of any insect in 0:02:14.760 --> 0:02:19.600 North America, seventeen year. Cicadas spend the earliest months of 0:02:19.639 --> 0:02:23.320 their final year burrowing towards the soil's surface. When the 0:02:23.320 --> 0:02:26.760 soil temperature rises above sixty four degrees fahrenheit or about 0:02:26.760 --> 0:02:30.520 eighteen degrees celsius, the cicada nymphs venture out of the soil. 0:02:31.080 --> 0:02:33.600 Their population may number a million or more in a 0:02:33.680 --> 0:02:36.320 space smaller than an acre less than half a hector, 0:02:36.600 --> 0:02:40.680 which helps survival rates. Animals ranging from spiders and birds 0:02:40.680 --> 0:02:44.240 to dogs and snakes find the lumbering cicada's easy prey, 0:02:44.639 --> 0:02:46.840 but will eat their fill long before they put a 0:02:46.880 --> 0:02:51.639 dent in the population. The then flightless young cicada's journey 0:02:51.720 --> 0:02:54.400 upward at sunset, crawling a foot or more up any 0:02:54.440 --> 0:02:58.239 nearby vertical surface tree trunks, weeds, woody shrubs, homes, or 0:02:58.280 --> 0:03:02.800 outbuildings to begin the next phase of life. Overnight, they'll 0:03:02.800 --> 0:03:07.080 shed their nymphul skins a much like the fictional Incredible Hulk. 0:03:07.240 --> 0:03:10.520 The cicadas will split their shell like clothing to unleash 0:03:10.680 --> 0:03:14.040 larger bodies, and as they emerge through the tops of 0:03:14.080 --> 0:03:17.280 their shells, the cicadas will unfurl their wings for the 0:03:17.320 --> 0:03:22.200 first time. Now the cicada is an adult, soft, ashen 0:03:22.280 --> 0:03:25.760 and vulnerable, waiting for its exoskeleton to harden and darken 0:03:25.880 --> 0:03:29.240 in color. It will leave its crunchy larval casing behind, 0:03:29.960 --> 0:03:32.840 still clinging to the cicada's first above ground resting place. 0:03:32.960 --> 0:03:35.520 The casing will be an empty and forgotten outline of 0:03:35.560 --> 0:03:40.400 the creature at once held. Not all cicadas appear on 0:03:40.520 --> 0:03:44.480 a strict schedule, though there are also some known as stragglers, 0:03:44.520 --> 0:03:47.160 that appear a year later or earlier than the rest 0:03:47.160 --> 0:03:49.960 of their brood. One year early or one year late 0:03:50.080 --> 0:03:52.760 is the most common time frame for stragglers, but this 0:03:52.800 --> 0:03:55.520 isn't always the case either. In the year two thousand, 0:03:55.560 --> 0:03:59.320 for example, many brewd ten cicadas appeared four years earlier 0:03:59.320 --> 0:04:03.320 than expected. It Some observers theorize that unseasonably warm weather 0:04:03.480 --> 0:04:07.080 may cause some stragglers to emerge early. Others suggest delayed 0:04:07.120 --> 0:04:12.040 development may cause some stragglers to arrive late. Scientists aren't 0:04:12.080 --> 0:04:16.040 exactly sure how cicadas no seventeen years or thirteen years 0:04:16.080 --> 0:04:18.600 have passed in the first place. They think it might 0:04:18.640 --> 0:04:21.320 have something to do with some property in the fluid 0:04:21.360 --> 0:04:23.440 that they suck out of tree roots for nourishment when 0:04:23.440 --> 0:04:28.479 they're underground, something that reflects the yearly cycle of the tree. Perhaps, 0:04:28.600 --> 0:04:32.040 if whatever this chemical signal is is weaker for insects 0:04:32.120 --> 0:04:35.200 under one type of tree versus another, that causes the 0:04:35.400 --> 0:04:40.920 off schedule appearances. Interestingly, the prime number appearances are thought 0:04:40.960 --> 0:04:44.040 to help with survival. Since the cicadas are not on 0:04:44.160 --> 0:04:46.760 the same two year or five year cycle as most 0:04:46.800 --> 0:04:49.960 of their predators, the predators don't become dependent on them 0:04:49.960 --> 0:04:53.520 for food. Stragglers who missed the big party are more 0:04:53.600 --> 0:04:57.960 likely to be eaten off. Periodical cicadas, whether they're a 0:04:58.000 --> 0:05:01.120 thirteen year or seventeen year species, will live for just 0:05:01.240 --> 0:05:04.080 three or four weeks above ground, only long enough to 0:05:04.120 --> 0:05:07.040 mate and, in the case of female cicadas, deposit eggs. 0:05:07.520 --> 0:05:10.160 This mate then die cycle is pretty common in the 0:05:10.160 --> 0:05:14.159 insect world. Male cicadas attempt to attract females with a 0:05:14.200 --> 0:05:17.480 loud buzzing that seems to undulate up and down between 0:05:17.680 --> 0:05:23.640 two distinct notes. Although each species of periodical cicada has 0:05:23.680 --> 0:05:27.440 its own song, the response of female cicadas varies little 0:05:28.000 --> 0:05:31.839 exactly one third of one second after the male's song ceases. 0:05:32.080 --> 0:05:34.760 A female responds with a click of her wings, but 0:05:35.000 --> 0:05:37.919 only if she wants him to make further advances. The 0:05:37.960 --> 0:05:41.040 male counters with the same call, hoping to hear another 0:05:41.080 --> 0:05:44.479 wing click. If he does, he makes two particular sounds 0:05:44.520 --> 0:05:47.679 in quick succession, awaits for a third wing click, and 0:05:47.720 --> 0:05:51.120 then it's on. Within about ten days, the female will 0:05:51.160 --> 0:05:54.520 deposit some four hundred eggs in small twigs and branches 0:05:54.560 --> 0:05:57.359 of nearby trees and shrubs, but choosing from among the 0:05:57.440 --> 0:05:59.880 eighty or so species that they prefer to use as 0:05:59.880 --> 0:06:03.920 an nurseries. The females have protruding needle like devices at 0:06:03.920 --> 0:06:06.400 the end of their abdomens, which are used to create 0:06:06.440 --> 0:06:09.960 an egg cradle in the wood. Female cicadas may repeat 0:06:10.040 --> 0:06:14.640 the egg laying process dozens of times. In about six weeks, 0:06:14.760 --> 0:06:17.680 white nymphs the size of ants will emerge from the eggs, 0:06:17.839 --> 0:06:20.280 drop to the ground and work their way into the soil. 0:06:20.960 --> 0:06:24.000 Like their parents, they'll spend the next thirteen or seventeen 0:06:24.080 --> 0:06:29.120 years feeding on fluid found in plant roots. Although cicada's 0:06:29.200 --> 0:06:33.080 root feeding is considered harmless, damage caused by female cicadas 0:06:33.120 --> 0:06:35.839 burrowing into trees and shrubs to deposit eggs can be 0:06:35.920 --> 0:06:39.560 significant twigs may break off, which can create production issues 0:06:39.600 --> 0:06:43.080 for fruit and nut orchards, and some caretakers cover small 0:06:43.120 --> 0:06:46.360 trees with mesh cloth to prevent access to bark. Others 0:06:46.360 --> 0:06:49.719 apply in secticides before egg laying occurs, or simply opt 0:06:49.760 --> 0:06:54.320 to wait out the cicada's limited lifespan. However, aside from this, 0:06:54.440 --> 0:06:57.960 these insects are generally harmless to plants and are harmless 0:06:57.960 --> 0:07:00.320 to people, so there's no need to panic if one 0:07:00.400 --> 0:07:04.000 lands on you. And what do you believe that cicada's 0:07:04.080 --> 0:07:08.000 make tasty high protein snacks? Apparently they taste like asparagus 0:07:08.040 --> 0:07:10.880 thanks to their plant based diets. The best ones to 0:07:10.960 --> 0:07:13.200 eat are those still in the nymph stage that don't 0:07:13.240 --> 0:07:15.840 have their hard outer shells yet. You can deep fry 0:07:15.920 --> 0:07:23.760 them and serve them with spicy sauce. Today's episode is 0:07:23.800 --> 0:07:26.640 based on the article why do seventeen years cicadas come 0:07:26.680 --> 0:07:29.960 out more often than every seventeen years? On how Stuffworks 0:07:29.960 --> 0:07:33.520 dot Com? Written by Lori Elda. Brain Stuff is production 0:07:33.520 --> 0:07:35.600 of I heart Radio in partnership with how stuff works 0:07:35.600 --> 0:07:38.280 dot Com and is produced by Tyler Clay. For more 0:07:38.280 --> 0:07:40.800 podcasts my heart Radio, visit the i heart Radio app 0:07:40.880 --> 0:07:43.520 Apple podcasts, or wherever you listen to your favorite shows.