by Lauren Alleman, M.S.
I can very clearly remember the last big cicada year that I experienced – it was summer 2003, Facebook didn’t exist and I was convinced I never needed to take organic chemistry (wrong). When you measure time in periodical cicada years, it is amazing how much changes.
If you’re an East Coaster reading this, do you remember what you were doing the last time you witnessed this fabulous entomological phenomenon 17 years in the making? If not, you have another chance this year to experience the incredibly loud humming and screeching sound of a brood of cicadas.
East Coasters from Virginia to New York are currently in the midst of a brood (a synchronized unit) of cicada nymphs emerging from 17 years of life in the subterranean feeding on the sap of tree roots. Amazingly, these nymphs emerge in the span of just several weeks in sync with one another. There are 12 surviving broods in the east today (several have died out over the course of this century). This year New York is anticipating the reemergence of Brood II.
There are seven species of North American cicadas that have a 17-year nymph cycle; although, some of these emerge after 13 years, perhaps the result of convergent evolution. There are other species of cicadas that emerge every 1 to 3 years, but not in the numbers that make us notice them.
For the phylogenetecist in my life who is near and dear to me (you know who you are), the periodical cicadas belong to the Order Hemiptera (the true bugs), Suborder Homoptera (the same suborder as leafhoppers and aphids), Family Cicadidae, Genus Magicicada that quite appropriately sounds like magic. These guys are different but frequently confused with locusts. Locusts are known for their destruction to agricultural crops; cicadas are relatively harmless.
The cicada life cycle is fascinating. After cicada nymphs crawl out of the ground and find a nice place to anchor their exoskeleton, they emerge into a beautiful winged creature that is destined to live just a few weeks in the sun, which is less than 0.01% of its entire life cycle. After a few days of adjusting to the light, cicadas get down to business; the males begin vibrating membranes in their abdomen to create a sound that echoes for miles and attract the lady cicadas.
It is amazing that evolution favors such a long subterranean life cycle and perfect synchronized timing. But according to evolutionary theory, cicadas emerge at once en masse to overwhelm predators to the point that their appetites will be sated (predator satiation), which allow many of adult cicadas to successfully mate and lay eggs in the twigs of trees. And so the cycle begins again, after the eggs hatch, the nymphs burrow into the ground for the next 17 years.
What will the world be like the next time Brood II emerges in 2030? Will Manhattan have a comprehensive strategy for protecting the city against future Superstorms? How different will the climate be? How many billions of people will inhabit our planet?