Bodies make noises. Think of all the noises your body makes — sneezing, coughing, singing, chatting, farting, yelling, clapping. That’s a lot of noise for one body! But it doesn’t even come close to the sheer loudness produced by one not-so-little insect, the cicada.
How do they do it? It all comes down to their body parts, or anatomy. But first let’s discover some basic cicada anatomy.
Cicadas are insects, which means they must have a head, a thorax and an abdomen. Like all other insects, they have six legs and two antennae. They also have four wings and compound eyes like most insects. Can you label the body parts on the diagram?
Abdomen: The rear section of an insect. It has nine to 11 segments.
Antennae: Two sit at the front of the head. They are used as sensors. They smell and sense touch, temperature and vibrations.
Compound eyes: Two eyes made up of lots of lenses. Cicadas have a wide field of vision, which is just a fancy way of saying they can see a lot more of the world without having to move their eyes.
Head: The top section of the body.
Legs: Six jointed legs. Scientists think they use some of their legs for digging or leaping.
Thorax: The midsection made up of three segments. This is where the legs are connected.
Wings: Two pairs (forewings and hindwings) attached to the thorax. It might look like they only have two wings when they are perched because of the way they fold back their wings.
There are a couple other cool body parts you might be able to see from the outside. Their mouthparts are called a beak. Look out for them tucked under their heads, looking like a small, sharp straw. It is perfect for sucking up plant juices!
They have three extra eye-type things on their head, called oculi. These eyes don’t really see, but they can sense light and dark. It’s like when you close your eyelids. You can still tell if the light is on in the room or if it is dark.
Go outside and scream as loud as you can. Do you think you can be heard from a mile away? Probably not. But tiny cicadas can! Even with no lungs and no vocal cords, a mass of cicadas in a tree can be as loud as a lawnmower. How do they do it? It comes down to their anatomy!
Our skeletons inside our bodies gives us shape. Like all other insects, cicadas don’t have bones inside their bodies. Instead, they have a hard exoskeleton covering the outside of their bodies. Imagine it like a knight wearing armor.
The exoskeleton includes two organs called tymbals. Look for one on each side of the abdomen, under their wings. The tymbals’ job is to make sound. Each tymbal has a bunch of ribs that are connected by a thin membrane. Cicadas flex their muscles, crunching down, and the ribs buckle one over the other. Every time a rib buckles, it makes a click.
Words to know
Anatomy: The structure of a plant or animal.
Exoskeleton: A rigid external covering for the body in some invertebrate animals.
Membrane: A thin sheet of tissue acting as a boundary, lining or partition in an organism.
Think of the bendy part of a bendy straw. Every time you move it back and forth, the ridges buckle over, making that weird noise. Try it for yourself! It’s like a cicada’s tymbal, just very slow. You could never move a straw as fast as a cicada can move its tymbals – 300 to 400 times per second!
How do cicadas make such loud noise by clacking ribs? They have air sacs in their abdomens that amplify, or expand, the sounds made by the tymbal. Basically, it’s like putting a microphone up to the bendy straw.
Different cicadas have slightly different sounds, from buzzing to low-pitched droning. You can listen to them at the Songs of Insects website.
Why do they go through all that trouble? Males are just trying to attract a mate! They buzz to woo a female, and they are louder when it is hotter outside. They also have calls to celebrate, distress calls and even a call to say, “Leave me alone!”
So now that you know this, go outside and listen to the beautiful sounds of the cicadas’ tymbals. Maybe bring your straw out to play along!
____________
Follow Willy's Wilderness on Facebook for more kid-friendly nature stories and activities.