Unique Cicada Cycles

The tall trees on the stately lawn of my grandparents’ farmstead supplied unmatched opportunities for children to collect spent “dog day” cicada shells. This common cicada variety is familiar to virtually everyone. We hear them every summer during August. There are many species of dog day cicadas which are barely distinguishable from each other except for their subtle singing variations and slight differences in appearance. The crisp, empty cicada shells supplied young people with childhood joy and plentiful “treasure.” Even more exciting was discovery of an emerging adult before it ascended to the tree tops to serenade the neighborhood for a few weeks.

Of nearly 3000 cicada species worldwide, only three species comprise the 17-year periodical cicada variety now receiving publicity as they emerge from the ground solely in the eastern United States. The unique timing ability of this creature is a rarity among cicadas worldwide. These three cicada species are included among the estimated six to ten million insect species on our planet. These millions of diverse species represent approximately 90% of all animal life. The extraordinary notoriety surrounding the 17-year periodical cicada is entirely warranted.

After remaining underground for 17 years, billions and billions of cicadas emerge when the temperature reaches 64˚F in their 17th summer. It is the longest-lived insect in North America, having tunneled underground out of sight while feeding on sap from tree roots. I have personally experienced three Brood II east coast emergences of the 17-year cicadas—1962, 1979, and 1996. In 2007 I also observed the singing of thousands of the same 17-year variety at our home in Illinois. It was Brood XIII, one of twelve broods in the US which overlap other 17-year broods. Most years the 17-year species emerges somewhere in the eastern United States. There are three or four “major” broods. The largest brood, dubbed Brood X, emerged in 2004 in 15 eastern states.

As if the 17-year cicada scenario were not interesting enough, there are several other cicada species which form three broods of 13-year cicadas. This variety’s counting ability stops at 13. The largest of the three broods, Brood XIX, last emerged in 2011 in 16 states including Illinois. The remaining two broods will not reappear until 2014 and 2015. In 2011, I believe I heard the faint songs of a few 13-year cicadas for a few days.

How do periodical cicadas keep track of their years underground? Some experimenters have attempted to fool a few laboratory specimens transplanted from the wild by forcing rooted indoor fruit trees to blossom twice per year. Apparently a few laboratory cicadas were tricked into emerging early. The insects, however, were still able to count fruiting cycles. Their mathematical talent for counting 17 cycles was still present in the insects. Beyond this, their ability to apply a difficult mathematical skill is still a mystery to scientists, but the ability is unquestionably programmed into the cicada’s genetic DNA blueprint.

Genetically programmed traits are ubiquitous in living things. Discussion of innate genetic markers and their relationship to the manifestation of physical traits is the subject of abundant research among scientists. Genetic traits also provide the organism with ability to acquire a multitude of learned behaviors. Base pair arrangement of molecules in DNA is responsible. This explanation is accurate and simple, but still inadequate: We translate the physical arrangement of molecular elements such as base pairs to time intervals of 17 or 13 years in periodical cicadas. But how could this be? Scientists do not know. The answer is in the omniscient mind of the Creator.

http://jasscience.blogspot.com/2013/05/unique-cicada-cycles.html