In the eastern half of the U.S., from small towns to big cities, the steady click of cicadas is synonyms with the dog days of summer. But what makes them click? And where do they go the rest of the year?
What a Life!
In the U.S., there are two primary types of cicadas: periodical cicadas and annual cicadas. Periodical cicadas burrow underground as nymphs and surface every 13 or 17 years. Annual cicadas emerge every year, usually around July and August.
Empty cicada exoskeleton
We only see and hear cicadas in the summer because they live most of their lives underground as a nymphs. When a cicada is ready to reproduce it digs a hole to the surface. Once above ground, the cicada sheds its skin. If you look closely in bushes or on tree trucks, you may even see the hard exoskeleton (shell) left behind.
After mating, the female drills holes into the bark of a twig and deposits her eggs. When the eggs hatch, the nymphs drop to the ground and burrow underground. This can happen for several cycles lasting two to five years.
The Symphony of Summer
So, what makes that unmistakable cicada sound? Male cicadas have membranes called tymbals on the lower outside area of their abdomen. Tymbals are part of the exoskeleton and act like drums. When a cicada contracts certain muscles, the tymbals bend inwards, producing a clicking noise. When the muscles are relaxed, the tymbals bend back to their original position, producing another click.
The hollow abdominal region of a cicada amplifies the sound. When a cicada clicks its tymbals quickly over and over again, the result is a steady, continuous note. The cicada can change the sound by changing the position of its abdomen. But why all the noise? Cicadas “sing” as a way to scare away enemies or to attract mates. Each species of cicada has its own distinctive mating songs.
Check out this video of a cicada singing.
10 Things You Probably Didn’t Know About Cicadas
- There are more than 3,000 species of cicadas around the world.
- The name comes from the Latin word cicada, which means “tree cricket.”
- Cicadas are not actually related to crickets.
- Cicadas are closely related to leaf hoppers and spittlebugs.
- Believe it or not, cicadas are edible (Yuck!). In fact, there’s a cookbook dedicated to cooking with cicadas.
- Cicada molt (empty exoskeletons) are processed and used to make traditional Chinese medicines, including supplements to treat sore throats, measles and tetanus.
- The song of the cicada is loud enough to cause permanent hearing loss if the cicada were to sing just outside the listener’s ear.
- Cicada nymphs use a long, tube-like proboscis under their heads to suck sap from various species of trees, including oak, cypress, willow, ash and maple.
- Although Cicada Killer Wasps pose no threat to humans, they can paralyze cicadas and use them to feed their own larvae.
- The largest species of cicada is The Empress Cicada of Southeast Asia. It is nearly three inches long and has a wingspan of up to eight inches.
Time to Explore
Try out these hands-on activities.
1. Search for cicada exoskeletons under ground cover, bushes or stuck to the trunks of trees.
2. Examine the exoskeleton under a magnifying glass or microscope (or take a closer look at the photos below.
Questions to ask:
- How many legs does it have?
- Is it heavy, light, soft, smooth, hard, bumpy? What color is it?
- How do you think it got out of the hard outer shell? (Hint: look for a split in the back of the exoskeleton.)
3. Make a sketch of your find in your field journal.
Books About Cicadas
Cicadas!: Strange and Wonderful
The Bizarre Lifecycle of the Cicada
Cicadas (Little Leaf Learning Series) Kindle Edition
Wikipedia – Cicadas
Chinese Herbs Healing