Entire regions of the United States are preparing, in these days, for an epochal event that occurs, punctually like a clock, once every 17 years, a fascinating and (relatively) harmless event: the awakening of the periodical cicadas (Magicicada septendecim), a species of the Cicadidae family whose life cycle foresees that the animal spends a month of life in the open air and seventeen years trapped underground, waiting for the right moment to return to the light. Virginia, West Virginia and North Carolina are the three states where all this happens in early summer.
17 years underground. Most of the life cycle of the periodical cicadas passes in the form of a nymph: in this phase they are sheltered 60 cm below the ground, and they use the roots of the plants to feed themselves. The more they grow, the deeper they go into the soil, in search of larger and more nutritious roots; they do it for 17 years (but there are species belonging to the same genus whose cycle is 13 years), after which, towards the end of May, when the soil temperature where they rest exceeds 17 ° C, they build pipes of mud that flows to the surface, and uses them to emerge. Once in the open air they go in search of a tree or another piece of vegetation to hide in, waiting for their exoskeleton to harden. At that point, when they become adults, they have a few weeks to reproduce, and at the end of summer they die, not before having “repopulated” the subsoil of nymphs, and having started the new cycle.
Laying 9. Not all specimens of Magicicada septendecim they emerge at the same time: the species is divided into broods, and the one that should appear in the United States at the end of May is the brood number 9. The last time the Magicicada it was seen in the USA it was 2013, with brood number 2: below, the video of the emergence of 2013.
Return of the Cicadas from motionkicker on Vimeo.
Finally, it is worth noting that the cicadas in question have been considered in the past as locusts, more for their ability to appear out of nowhere in huge numbers than for the real damage they do: their eating habits can endanger survival of some young trees, but the damage to human activities is limited. What they really stand out for is the noise they make: according to Virginia Tech experts, the sound of millions of cicadas singing simultaneously is «How to listen to an entire field of radio frequency».