17 was a great year

Jul. 17, 2013 @ 05:00 AM

You may have seen a few around this year. Hanging from a low limb or attached to the side of a tree; I'm referring to those small empty brown shells that once contained a cicada nymph.

As a child I was fascinated by these shells and would even collect them to keep in a basket atop the refrigerator.

Only once or twice did I happen upon an actual adult cicada not realizing what the connection between the two actually was.

But summer after summer I began to notice something.

The next year and the following, it would be nearly impossible to find any shells; as if they had just vanished. Little did I know that I wasn't far off in my assumption. It would be many years later though before I would realize what was going on around and under my feet.

Allow me, if you will, to provide a brief summary of the cicadas fascinating life-cycle.

As stated earlier the brown shells contain the nymph, or young cicada. They are buried underground anywhere from 6 to 18 inches. Usually found under trees, the younglings survive from sap provide by the tree's roots.

Now here's the kicker, the nymphs aren't just there for a few months or a year but more impressively they remain underground, sucking on sap, for 17 years.

With the arrival of that 17th year they, all at once, begin their journey to the surface by digging forward with their powerful claws. Emerging in the thousands they head straight for the nearest tree to ascend it's bark looking for the perfect spot to lock in and begin the molting process, or shedding of their outer skin.

Soon the adult cicada finally emerges with bulging red eyes and large ribbed wings. Cicadas do not sting or bite and have no interest in bothering or interacting with anyone. Their main focus is to find a mate; and after 17 years underground, time for them is almost up. For the adult cicadas only have 4 to 6 weeks left in their lifespan and each precious second is used in the creation of the next generation, or brood of cicadas.

You will know if things are underway in the trees for the mating process provides one of the loudest soundtracks to all of nature. The males generate a distinctive loud buzz that is intended to draw the female near, where she replies with an equally loud clicking sound made by the flick of her wings.

After all the mating is done the females will lay their eggs in a branch or small twig. Then just as quickly as they emerged, all the adults begin to reach the end of their lives.

This end of life also marks the begging, as within the next 6 to 10 weeks the small eggs, about the size of a grain of rice, hatch into new nymphs that will fall from the limbs onto the ground where they instinctively dig down to remain for another 17 years.

Thus the cycle starts all over again.

But how do cicadas know when 17 years are up without a watch?

The thought is that somehow they can determine the passage of time by changes in the tree's sap. However they do it, it continues to work and remains one of the insect world's most impressive wonders.

OK, the science lesson is over.

For a nature geek like me I find this fascinating.

But why is this important?


Looking online I have found that this year, 2013, marks the start of the return of what entomologist refer to as Brood II. Last see in 1996 this large group of cicadas span from North Carolina up the eastern seaboard.

The periodical cicadas are grouped into broods based on the calendar year when they emerge and are provided a Roman numeral that correlates with each individual broods.

It looks like the next best time for this area to see massive amounts of cicadas will be with the emergence of Brood XIV in 2025, last seen in 2008.

So go ahead and mark your calendars folks and if you happen to be out this summer and find any shells from Brood II hanging around, well now you know where they came from.