Posted by: Sand Squiggles -- Richard Modlin's Blog | May 10, 2011

17-Year Cicadas are Back

 

Marian and I had a pleasant surprise this past Sunday morning (May 8, 2011).   During breakfast in our sunroom, we noticed about a dozen little cicadas, outside, sitting on the deck’s banasters and chairs, drying their wings. Nearby, were the nymphal exoskeletons these bugs left behind after molting into the adult stage.  

Seeing these insects hit me as strange, because cicadas are the noisy harbangers of late summer—and it’s only mid-Spring.  And these guys were not the bombastic green bugs we hear and see in August and September.  Instead, they were attractive little creatures of about 1.0-1.2 inches long with brownish-gold wings streching away from a gnarly black thorax and a pair of large cherry-red eyes. 

Then it dawned on me.  I had seen this species of cicada before, in the spring of 1994.  There were hundreds covering the trees in a yard of a house I previously owned on the south side of Huntsville, Alabama.  Back then, I did what any field biologist would do.  I collected a bunch, identified the critters and showed them to my invertebrate zoology class.

“I’ve seen this happen before,” I yelled, “seventeen years ago.  By golly!  What we’re seeing is the emergence of the periodic 17-year cicada, Magicicada septendecium.  Get the cameras.  This won’t happen again until 2028.”

Unlike the big 13-year and non-perodic green cicadas that vibrate our eardrums on late summer evenings, this species lives 99.9% of its life as a nymph 10 inches underground for seventeen year, feeding on the juices of plant roots.  When the nymphs fully developed, they wait until the ground temperature at the depth they resides reaches around 63o F, then they burrows their way to the surface enmass—the entire brood in an area (hundreds and sometimes thousands of them) emerges within a day or two. 

Nymphs dig an escape tunnel of about a quarter inch in diameter and crawl out onto the surface of the ground.  Then climb up some nearby prominence and molt.  After exiting their nymphal exoskeleton, the nymphs amble to a safe place safe and dry their bodies and inflate the wings—a process that takes about two hours.   The adult cicadas then fly into the trees where they mate.  

To attract females, the males “sing.”  Their song is loud and intense.  Receptive female respond by flapping their wings in time with the males’ chorus.  Females usually mate once, but multiple matings with a single female does occur.  After mating the female cuts a slit in a young tree branch and lays about twenty eggs.  She does this several time, laying a total of about 600-700 eggs.  After mating adult males and females die.  The entire adult portion of the 17-year cicada lasts about ten days to two weeks.  By the end of June the forests around Hunsville quiet down.  Only the subtle songs of birds, and the chirps of crickets and kadydids touch our ears.

Cicada eggs hatch in about six to ten weeks.  Newly hatched nymphs, which are about the size of a pinhead, drop to the ground and burrow in.  They will grow in the subterrian habitat and reemerge again in seventeen years.

© Richard Modlin 2011


Responses

  1. Very interesting, i love these bugs,they ring in your ears for hours, all the while i’m thinking how lucky my life span is so much longer; animal behaviour rules:)


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