It’s only at this time of year in northern Illinois that we get to hear the changing of the “chorister” guards as day melds into night. In the heat of the day, annual or dog-day cicadas screech from the tops of trees. Some of them lingeri in their singing until dusk just as the crickets begin chirping from below.
When I hear these sounds, I’m taken back to the days when my sister and I were visiting our aunt and uncle. We swam in the pool during the day as the cicadas whined. Then when we went to sleep with the windows open, the crickets’ songs lulled us to dreamland.
Crickets and cicadas are both insects, but each with its own lifestyle and method of singing.
The crickets we hear outside our doors are probably the non-native variety called house crickets, which likely came from Asia. Other native crickets can be heard in prairies and woodlands at night.
Male crickets create the chirping like song by rubbing a scrape-like structure on the left wing against the teeth of a file-like structure beneath the right wing. They sing to attract females, who will lay up to 700 eggs. Many of these eggs get eaten, but those that don’t hatch into young crickets. Crickets eat other bugs as well as plants. They spend the winter holed up in a warm place outside, and emerge when the temperature rises in summer.
It’s been said that you can tell the temperature by counting the number of times a cricket chirps within a given amount of time. It’s true – even Snopes.com agrees that if you count the number of chirps a cricket makes in 14 seconds, then add 40, you’ll get the approximate temperature. I tested the theory on a cool summer night. I counted about 14 chirps in 14 seconds the other night and added 40 to come up with 64 degrees – and that was just about right.
The reason crickets and cicada songs only overlap this time of year is because cicadas aren’t nearly as vocal if the temperature isn’t around 80 degrees. As the temperatures decline in fall, we can still hear crickets, but the cicadas die out. We’re still having some days above 80 degrees – and that’s when we get to hear both insect songs overlap.
The cicadas we’re hearing now are annual cicadas that emerge each summer to mate and produce young. About 2,500 species of cicadas live in the world – most of them have large eyes far apart on the head and transparent, veined wings. Some of them have three more tiny eyes in between the large eyes. The cicada uses its long proboscis to suck tree sap.
When male cicadas sing, they aren’t rubbing two structures together like crickets do. Instead they have tymbals, muscles that they vibrate to create the high-pitched whirring sound. Each cicada species has its own song.
Cicada females lay several hundred eggs in the bark of a twig. When the nymphs hatch, they drop to the ground where they bury themselves sometimes 1 foot or more below the surface. They’ll remain there feeding on root juice, sometimes up to five years before emerging back up and shedding a shell, then crawling up a tree to begin a new life as an adult. They’re called annual cicadas, because we hear them every year. But the cicada screaming now might have spent several years underground. The species of cicadas that stay underground for 17 years before emerging arrived in droves in northern Illinois. They emerged here in 2007 and won’t be out again until 2024.
The lives of crickets and cicadas are fascinating – but I forget about all that at night when the sound of a cricket seems almost magical as it lulls me to sleep.