We all know the cicadas are coming. The story has been all over the local media in the DC area. I have not heard the shrill notes of a male cicada yet, but the edges of our garden are pocked with tidy circular exit holes bored up through the earth by eager cicada nymphs. Eager, but not too eager. Each nymph remains underground, getting ready to climb up out of its hole, clamber up onto a branch, and crack out of its exoskeleton, emerging as a fully-formed adult of the Brood X periodical cicada.
For most Washingtonians, periodical cicadas are bugs, and most humans do not appreciate bugs. Cicadas do not bite or sting, but their grasping feet are prickly and the vast numbers and the noise seem to frighten normal citizens unused to insect abundance. Naturalists, on the other hand, love the cicada emergence, and are in awe of that seventeen-year cycle. I am a naturalist, so I have been anxious to experience another natural mega-event that makes an indelible time-stamp at yet another stage of my life.
It is the cicada emergence that reminds me, like no other event, of the finite nature of human life, reminding me that, as with the cicadas, I will do my thing and then inevitably shuffle off this mortal coil. That is humbling and makes me think about my periodic interactions with these magical and noisy creatures. The cicada story has been an integral part of my 69 years on this planet.
In May 1953, as a two-year old living in Baltimore, I happily consumed cicadas as I crawled about in the front lawn of our home (or so I was told by my mother). In May 1970 the cicadas appeared when, as a senior in high school, I was doing an independent study of bird migration with classmate Bill Johnson, mist-netting migrant songbirds in suburban Maryland under the tutelage of Gladys Cole. The appearance of the cicadas was overwhelming and unforgettable. In May 1987, ensconced in Bethesda, I recall our next-door neighbor spraying his hedge with insecticide, and my visiting mother upbraiding the hapless man, saying “Don’t be a fool! The cicadas are harmless.” Finally, in May 2004, I recall driving out in suburban Virginia with birding friend Stacey Maggard, with the droning of the cicadas as loud as I ever heard them, making it difficult to chat inside our air-conditioned car traveling at 65 miles per hour.
Now a new memory will be forged by the next emergence of the red-eyed hemipterans. What might that memory be? Time will tell, but there will be one, for certain. This will be cicada emergence number five for me. If I am lucky, I might get to experience emergence number six in May 2038, when I will be 86. I do not expect (or want) to be around for the emergence in May 2055 (who can image what the world will be like in 2055?).
There are not many natural phenomena that regularly occur on a scale as long as 17 years. The famous lynx-hare predator/prey abundance cycle takes place on a 10-year cycle, but it is not nearly so predictable as that of the cicadas. The cycle of the spruce budworm outbreaks in boreal spruce-fir forests is approximately 30 years between peaks, but with a lot of temporal variation. But these and many other natural cycles do not inform our collective memories in the manner of the periodic cicada.
The simplest biological explanation for the 17-year cycle of the cicada is twofold. The long interval between emergences “starves” the many species of birds as well as squirrels that greedily prey upon the bugs, so that most of the emerging cicadas survive the onslaught. The 17-year periodicity (a prime number), prevents the predators from timing their abundance cycles by shorter, evenly-divisible cycle periods — preventing the predators from cracking the 17-year “code.” The theme is “starve the predators” for 17 years and then satiate them for a brief few weeks in May of that last year. Another well-known periodical cicada recurs on 13-year cycles — using another prime number.
As a biologist, I love the deployment of a prime number and the interplay of mathematics and species life history. But as a naturalist, I appreciate the life-and-death story that the cicada tells us. This creature spends seventeen years as a nymph burrowed underground, patiently sucking sap from tree roots and watching the clock for the coming of the big day (waiting 6,029 days when counting leap years). The adult cicadas that suddenly appear in our neighborhoods sing, mate, and lay eggs in tree twigs, living the entirety of their above-ground lives in a brief month before they die. Thus the cicada’s life is a reverse of a human life, in which childhood is relatively brief and adulthood is long. The cicada’s brief adulthood, reminds us that, in fact, in the great scheme of things, our adulthood is, indeed, brief, and that the end comes all too soon. It is a reminder that we should all seize this very day, for who knows what tomorrow might bring? So let’s all forget our inhibitions and fears and enjoy this very special event, when our neighborhoods will be taken over and dominated by another species — something that does not happen much any more in our human-dominated world.
Bruce Beehler is a local naturalist and author of 12 books, including “Natural Encounters,” and “Birds of Maryland, Delaware, and the District of Columbia.”