Seventeen-Year Cicadas are Back! (in Iowa, at Least)

I traveled to Iowa this week (more on that next week) and just happened to arrive during the emergence of one of the world’s most intriguing insects – the periodical cicada (Magicicada sp).  Made up of seven different species, periodical cicadas are found only in eastern North America and are named for their long life cycles of either 13 or 17 years.

This newly-emerged cicada (Magicicada sp) hadn't completely dried out yet, so it's wings weren't functional enough to fly away from me.  I put it on a stick for an easy photograph.
This newly-emerged cicada (Magicicada sp) hadn’t completely dried out yet, so it’s wings weren’t functional enough to fly away from me. I put it on a stick for an easy photograph.

All cicadas (that I know of) spend most of their lives underground as larvae before emerging for a brief, noisy life aboveground.  What makes periodical cicadas unique is not so much the length of time spent as larvae – though it’s longer than other cicada species – but rather the synchronization of their emergence.  The common dog-day cicada, for example spends multiple years underground as a larva, but we see adults every year because their emergence is staggered across years.  In contrast, periodical cicadas synchronize their emergence so the entire population in a particular area is on the same schedule.  That timing of emergence, however, does vary by region across North America, so while seventeen-year cicadas are out in Iowa, Illinois, and Missouri this year, they emerged last year in an area covering states including Maryland, New York, and Virginia.  People living in eastern Nebraska will get a chance to see them in 2015.

Emerging as adults in hordes probably helps ensure the survival of individual periodical cicadas (and their species) because predators can’t eat nearly enough to put a dent in the population.  If periodical cicadas showed up in huge numbers every year or two, there would surely be predators with life cycles timed to take advantage of the abundant food source.  However, the extreme length and synchronization of the cicada life cycle has apparently kept any predator species from being able to take advantage (evolutionarily) of the phenomenon.  Fortunately for us, cicadas are harmless to people, and even the damage they do to trees by feeding and laying eggs in stems is almost always temporary.

There is much more fascinating information about periodical cicadas, but others have already covered it far more completely than I can.  If you’re interested, I strongly encourage you to visit the magicicada.org to learn more.

 

7 thoughts on “Seventeen-Year Cicadas are Back! (in Iowa, at Least)

  1. Tom P June 5, 2014 / 7:30 am

    Cicadas cycles are great opportunities to introduce kids of all ages to the art of eating insects! They are full of fat and protein and have a neutral taste taking on the flavor of what ever you cook them with. Our favorites were garlic and soy sauce :)

  2. Mike Suiter June 5, 2014 / 7:41 am

    Last summer the barred owl pair around us would perch in our yard in late evenings. They would drop down to the ground, eat something, then back up. This happened for about 2 weeks and we think they were eating cicadas.

  3. anastaciast June 5, 2014 / 2:11 pm

    Thank you for this post. I sure needed something cheerful to read today.

  4. Nature Boy June 10, 2014 / 10:04 pm

    Thanks for the link to magicicada. I saw a bunch of cicadas outside Des Moines this last Sunday evening at Yellow Banks Park. They were drying their wings so we got an up close look. I’ll be watching for them in NE next year.

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