You may have seen news a couple of years back about a massive swarm of cicadas suddenly appearing out of nowhere across several eastern U.S. states. The event appears as if it’s pulled directly from fiction, with bystanders noting hundreds of little winged insects crawling out of the ground and flying in groups.
Fear not, however. For one, these insects are relatively harmless. These insects only ever “drink” from trees, meaning crops remain safe. Lastly, these insects quickly die off almost as soon as they appear, as they rise from the ground simply to look for mates.
The Who
These cicadas, specifically members of the genus Magicicada, may appear gone for now, but the eggs that those cicadas from years ago made will be back to take over the skies once again—you just have to wait some 17 years or so.
The seven members of this genus all undertake this expansive 17-year life cycle as they go through larval, nymph, and adult stages. Furthermore, this particular strategy of appearing in vast numbers is more than just a way to increase the success rate of finding a mate.
The How
The story starts with the serenades of male cicadas, who use specialized structures in their bodies called tymbals to produce their distinctive high-pitched mating call. Females lured in with these songs eventually mate with them and produce eggs within the twigs of trees, particularly woody plants.
Once these cicada nymphs emerge from the eggs, they descend underground and attach themselves to tree roots. From there, they extract and get their nutrients from tree sap. The nymphs use the energy they gain from the roots to undergo multiple molting stages over several years, with each stage designed to grant them larger and larger exoskeletons to compensate for their growing size.
Finally, roughly 17 years after they hatch and descend underground, the now fully-grown cicadas emerge, flying away in massive swarms to seek mates and begin the cycle anew.
The Wrap-Up
Some experts have raised some unique explanations for why these cicadas “hibernate” as long as they do, ranging from effects from the previous ice age to the cicadas counting host seasonal cycles, among other attempts. Whatever the true explanation may be, what we know is true is that these insects have used this very strategy to survive to the present day; it definitely “works” in that sense.
They also claim that these insects appear in numbers as large as they do to overcompensate for whatever loss their population experiences due to the presence of their predators—a process known as predator satiation.
Overall, these cicadas are a marvelous display of organisms adapting to the environment in spectacularly unique ways—a spectacularly long-winded way, sure, but unique.
References
- Emergence of the 17-year cicada. (n.d.). Retrieved 22 September 2023, from https://extension.entm.purdue.edu/cicadas/
- Gornstein, L. (2021, October 12). Brood X cicadas emerge after 17 years to swarm the Northeast (Warning: Graphic images). CBS News; CBS. https://www.cbsnews.com/pictures/brood-x-cicadas-emerge-after-17-years-to-swarm-the-northeast/
- Karban, R. (1986). Prolonged development in cicadas. In F. Taylor & R. Karban (Eds.), The Evolution of Insect Life Cycles (pp. 222–235). Springer US. https://doi.org/10.1007/978-1-4613-8666-7_14
- Karban, R. (1997). Evolution of prolonged development: A life table analysis for periodical cicadas. The American Naturalist, 150(4), 446–461. https://doi.org/10.1086/286075
- Karban, R., Black, C. A., & Weinbaum, S. A. (2000). How 17-year cicadas keep track of time. Ecology Letters, 3(4), 253–256. https://doi.org/10.1046/j.1461-0248.2000.00164.x
- Nelson, L. (2004). Big buzz as cicadas arrive after 17-year gap. Nature, 429(6989), 233–233. https://doi.org/10.1038/429233a
