Many cicadas fail their final molt and die, cutting short a 17 year marathon within sight of the finish line.
Last week we talked about a trickle, but not a flood of cicadas, here in the DMV. A few days in the mid - 70s with showers here and there changed the situation rather dramatically. In many areas in northern Virginia, Maryland, and DC hordes of cicadas appeared over the past several days. As the vanguard of Brood X arrived in fifteen states ranging from Georgia to New York in the east and states bordering the Mississippi to the west, their strange strategy for survival, predatory satiation, dramatically took center stage in millions of backyards. While annual cicadas depend on stealth and speed to survive, periodical cicadas play a bizarre “safety in numbers” game. By emerging by the billions almost simultaneously, they fill the bellies of every predator that wants to eat them and yet enough survive to perpetuate the three species known as Brood X.
During the next three weeks, billions of cicadas will make a jailbreak after seventeen years underground. The lucky ones will join a tidal wave of other nymphs as they ascend trees and other vertical structures at night. This late riser successfully shed her exoskeleton in the waning hours of night. After ascending the tree at dawn and pausing to expand her wings on the shell of a brood mate, she must wait several days for her body to harden before flying to the treetops to find her mate.
Do cicadas really grow on plants?
While holding a record for the longest juvenile period of any insect (termite queens live a longer adult life span at more than 50 years), they escape above ground predators for 17 years. However, their interment underground while sucking on plant roots comes with its own perils. Three ancient oaks in a nearby park spawned thousands of cicadas in 2004. Five years ago, two of these veterans were removed and the root systems subsequently died. Conspicuously absent around the stumps this spring were any signs of cicadas or their exit holes. At the base of the remaining giant, another bumper crop of cicadas has made their appearance. Development also imperils cicadas beneath the earth. Homes, parking lots, driveways, office buildings and other forms of human development supplant trees with impervious surfaces, the death knell for cicadas. On the micro-level, even patios and stepping stones in a garden can prevent these teenagers from enjoying their brief moment in the sun.
Death comes in many forms to Brood X cicadas. Impervious surfaces like garden pavers prevent the nymphs’ escape from the earth. Pathogens kill many nymphs underground prior to emergence. Fierce carpenter ants feast on helpless newly molted adults on the night of their disinterment. Woodpeckers, grackles, mockingbirds, flycatchers, sparrows, and many other birds and small mammals, including foxes and squirrels, devour cicadas by night and day. Clumsy nymphs ready to molt latch onto their kin, dooming themselves and their brood mates. Watch as one nymph dislodges another, sending it to a certain death on the ground below, a comical yet tragic ending to seventeen years underground and an almost completed life. Images of squirrel and grackle by Dan Gruner; Jack Bush provided the nighttime image of a fox.
The biggest winners in this game of life and death are all the creatures higher up the food web that benefit from the bounty provided by periodical cicadas. For the vanguard of cicadas storming the world above ground, the carnage will be great. Foxes, raccoons, squirrels, and dogs spent the last several weeks unearthing delectable cicada nymphs. Birds and non-feathered reptiles are feasting. Periodical cicadas are a bounty for many species of birds, a banquet resulting in larger clutches of eggs, shorter inter-clutch intervals, higher nestling body mass, and higher fledgling success during this year’s emergence of periodical cicada. In my neighborhood a pair of nesting hawks spends their afternoons swooping down to lawns below to catch cicadas and return them to a nest with some very healthy looking eyas.
Unfortunately, this run of moderately warm days with unusually chilly nights seems to have taken an unusual toll on cicadas. Many nymphs emerging from the earth near dusk with temperatures in the upper 60s, hit a developmental brick wall as temperatures rapidly dropped to the low 50s and 40s during the night. Failure to complete the process of shedding their nymphal skin seems to be accounting for unusually high levels of molting failure and death in these early risers. But for Brood X in the mid-Atlantic, good news may be just around the corner with a forecast of daytime highs in the 80s and nighttime lows in the 60s. Get ready for teenagers rockin’ in the treetops by this time next week.
Acknowledgements
Bug of the Week thanks Randy for allowing us to visit her cicada sanctuary and Dan Gruner and Jack Bush for providing images. Two great references “Reproductive responses of sparrows to a superabundant food supply” by T. R. Anderson, and “Effects of superabundant food on breeding success and behavior of the red-winged blackbird” by C. E. Strehl and J. White were used to prepare this episode.
To keep current on what’s up with the 2021 Brood X cicada emergence in the DMV, check in with the Cicada Crew at the University of Maryland.