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Neat to know ~ Creature of the week

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Periodical Cicada, Washington D.C.

Photo: Katja Schulz, CC BY 2.0

Cicadas

2021-05-17

Cicadas can be found on every continent except Antarctica.  There are more than 190 different kinds in North America alone, and around 3,400 varieties globally.  This number is growing, though, as scientists find more and more distinct species and subspecies.

All cicadas fall into one of three groups.  Annual cicadas have a one-year life cycle and make an appearance every year.  Their chirps and buzzes are an iconic sound of summer in various parts of the world.  Periodical cicadas are born above ground but then dig into the earth and stay down there for years.  All of the cicadas that were born in a certain year will emerge from their underground homes at the same time.  Protoperiodical cicadas often come out every year, but occasionally, many different types appear simultaneously.

At some point in May 2021, a periodical species of cicada will surface after spending the last 17 years underground! 

Read on to find out more about these unusual creatures and the dramatic appearance they will soon be making!

What is about to happen?

– Any day now, trillions  -yes, trillions – of periodical cicadas (which are only found in North America) will surface in several states across the midwestern and eastern United States.  These insects are all members of what is being called “Brood X” (say “Brood Ten”).  They were born in the same year and have been spending the last 17 years underground, feeding and waiting for the precise moment at which they would all emerge at once.  That moment is almost here.

– The cicadas will stick around for just a few weeks, feeding and mating, and then, all of Brood X will promptly die.

– The Brood X cicadas have black bodies about the size of an adult’s thumb.  They have wide-set, bulging, red eyes.

– It is still a scientific mystery why periodical cicadas, like the ones many of us will soon see, emerge all at once in such staggering numbers.  But many entomologists (scientists who study insects) believe that this is part of a survival strategy.  If there are trillions of insects, predators like snakes and birds will not be able to make much of a dent in the population, even if they eat as many cicadas as they like.  In this way, cicadas can ensure that enough of their kind will be able to mate and reproduce.

The Extraordinary Lifecycle of Periodical Cicadas

– Cicadas start out as tiny eggs that are about the size of rice grains.  A female cicada will lay her eggs on trees in special tiny trenches that she carves into tree branches.  Here the eggs are protected.   After making sure her eggs are securely deposited, the female cicada will fall back down to the ground and die.  A single female cicada will lay up to 400 eggs and place them in numerous trees within an area.

– It takes 6 to 10 weeks for the young cicadas to hatch from their eggs.  When they do, they immediately begin to eat the nourishing fluids that they take from the tree on which they were born.  The cicadas grow quickly, and when the time is right, they leave the tiny groove in which they had been born, and tumble down to the ground.

– A young cicada will then begin to burrow into the earth, in search of roots on which to feed.  It will remain underground for years.  What does it do down there?  Mostly eating and tunneling.

– After 2 to 17 years, periodical cicadas will resurface.  At that stage, they are called nymphs.  They wait until the soil temperature is right around 65 degrees F (18 degrees C).  As soon as they emerge, they find a plant or other object to climb up.  There they cast off their exoskeletons.  Their wings grow a bit as they are released from the hard shell that had encased them for so many years.  Now they are adult cicadas.

– Adult male cicadas spend their time above ground looking for mates.  Most of the loud chirping and buzzing that one hears in the summertime in certain parts of the U.S. comes from the male mating calls.  Cicadas have special organs called tymbals which they move back and forth with tiny muscles to create a loud, vibrating sound that should ultimately attract a mate.  After females respond and mating takes place, the mothers-to-be look for suitable places to deposit their eggs.  Meanwhile, the male cicadas die. 

– The appearance of so many cicadas all at once can be startling.  But they are not harmful or dangerous in any way.  Cicadas are sometimes confused with locusts, but the two are completely different.  Locusts are a kind of grasshopper.  They devour the vegetation all around them, often decimating entire crops and causing ruin to farmers.  Cicadas, on the other hand, live off of sap, which they take from roots and tree branches.  If there are lots of cicadas all feeding in one area, fragile saplings could be overwhelmed and suffer significant damage.  More mature trees, however, aren’t usually damaged at all. 

– If you happen to live in an area that will experience the emergence of Brood X, be curious — not afraid or repulsed!  Closely observe these amazing creatures that have lived just beneath your feet for more than a decade.  Then take a moment marvel at nature’s grand design.

Sources: Katzman, Rebecca, Time.com, “Trillions of ‘Brood X’ Cicadas Are About to Emerge Across the U.S. to Sing, Mate and Die.  Here’s What to Expect,” https://time.com/brood-x-cicadas/, April 14, 2021; National Geographic; Cicadas: facts and photos; https://www.nationalgeographic.com/animals/invertebrates/facts/cicadasCicadamania; “Latest Cicada News,”  https://www.cicadamania.com/, May 16, 2921; Katz, Leslie, Cnet, “Brood X cicadas start to emerge across the map: What to know right now,” https://www.cnet.com/how-to/brood-x-cicadas-start-to-emerge-across-the-map-what-you-need-to-know-now/, May 14, 2021.