No doubt you have heard plenty of news stories about the 17-year cicada emerging this year. I have yet to see or hear them in my area yet, but I look forward to hearing the male cicadas’ persistent and often loud chorus.
The combined drone of thousands of cicadas singing at once hides the fact that there are three species of cicadas out there, each singing a different song, which chances depending on the proximity to a possible female mate.
More on cicada songs later, but first let’s review the odd lifestyle of the cicada. It’s mostly spent in the dark, with cicada nymphs living in the soil sucking sap from plant roots and waiting the long years away. They start out about the size of an ant, but over the years grow to be around two inches long.
This is a slow process (17 years remember) that involves the nymphs going through five stages where they shed their exoskeletons as they grow. So how do they know when 17 years is up and it’s time to come out go to the party? Researchers still don’t know.
It’s possible that they have a thermometer of sorts, and they keep up with the number of times the soil warms up each spring and come out on the 17th warm up. Some miscount and come out the wrong year, when you’ll hear pretty lonely cicada singing for naught.
When that 17th spring arrives and the soil temperature hits 64 degrees, out the cicadas come by the thousands. They climb up on a branch and molt off their old exoskeleton and climb out of it as adults. These old skins can be seen all over the place in high population areas. The brand-new adult must wait a few days for their new skin to harden, and then the males sing their buzzy love song, find a female and mate.
The female then flies to a tree branch, cuts a slit in it with a needle like tool on her rear (an ovipositor), and lays around 20 eggs in it. She will repeat this several times and can lay hundreds of eggs. In around 6-10 weeks the eggs hatch and the small nymphs drop to the ground and burrow in and begin another 17-year cycle.
Now back to the singing, which to us just sounds like a continuous buzzing. But as mentioned earlier, there are three species of cicadas out there and each sings a different love song. And the male varies his particular song when a female seems interested. One cicada species you may have heard individually has a song that starts out in a long high pitch that then suddenly drops to a lower and shorter pitch.
It’s one that I was told as a child is saying “pharaoh”, as in the Biblical plague of locust pharaoh. It starts out with a long phaaaaaah and then drops to a short “row”. He’ll fly around singing this same song, and suddenly he hears a clicking noise a female makes with her wings, indicating she is interested. At that point the male changes the song to a rapid-fire series of “pharaoh-pharaoh-pharaoh” notes until he finds the female.
He then sings a different (no doubt a happy one) song during mating. So all this is going on and we totally miss the complexity of their singing because many thousands of cicadas per acre are doing the same thing and all we hear is a group chorus that seems to be one steady and loud buzzing note.
This 17-year cycle gives the periodical cicada the record as the longest living insect. The adult cicadas are heavily fed on by a variety of predators, from snakes to humans, but there are so many of them their population does not suffer.