Why are Aussie cicadas so loud on hot, summer days? You’d be screeching too if, after seven years underground, you only had a few weeks to find a mate before you died.

 

A cicada hanging on to a a blade of grass where its recently shedded shell is also hanging.

The Sandgrinder coming out of its shell. Pretty sure it’s named after one of Spiderman’s villains. For those playing at home, it’s also known as Arenopsaltria fullo. Image: Kerry Stuart

Summer doesn’t officially kick in until you are deafened by a cacophony of cicadas desperately screeching for a mate. You might be frantically fraternising too if you’d spent up to seven years underground sucking on tree sap and you’ve only got a week or two to shed your exoskeleton and get the attention of a female — among the thousands of others just like you — without getting eaten. It’s a tough gig for male cicadas.

Cicadas (pronounced se-cade-ahs, in our humble opinion) are a truly iconic part of Australian summer and despite some species being capable of producing an ear-splitting call so loud it’s painful for human ears (over 120 decibels), they tend to be a much-loved insect. Perhaps because their calls signal long, lazy summer days or perhaps their expert camouflage and mysterious shells captured our imaginations growing up. Either way, they’re an integral part of our Aussie lives.

Summer sounds

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Cicadas hold the record for the loudest insect in the world. While every species has their own special call, many use the same tactic to increase their chance of finding a mate while avoiding predators: they group together and sing in chorus. The logic is similar to why fish swim in a big school; by being noisy all together, they hope that the many predators that crave the crunch of cicada (such as birds, ants, spiders and even bats) pick one of their noisy neighbours instead of them. The collective sound is also painful and discombobulating for many predators. The time of day they sing is also no accident: during hot, oppressive weather most predators are too busy trying to keep cool to go hunting. Pretty clever, huh?

So how do such tiny creatures make such overpowering overtures? Scientists are still trying to figure it out fully but the general gist involves a pair of ribbed membranes on the abdomen called the tymbals. The male cicadas contract the muscles in their abdomen (called internal tyrnbal muscles) which causes the tymbals to collapse inwards, creating a pulse of sound. When male cicadas sing, their ear-parts (called tympana) also crumple up so they don’t deafen themselves. Fun fact: While you’d be used to hearing the larger, very loud cicadas, some smaller cicada species are known to also sing loudly, but at a pitch too high for us to hear!

Naming rights

Cicadas certainly are a favourite insect of children. In fact, many new species in Australia have been discovered by tiny tots who have doggedly searched for the source of that strange sound. This has led to many adorable common names for Australian species including Black Prince, Yellow Mondays, Greengrocers, Floury Bakers and Cherry Nose. With many hundreds of new species of insects being found around the world every year, there’s every chance there are more creative cicada names to come: so keep your eyes peeled, your camera ready and document your findings on the amazing Atlas of Living Australia website. If you find a particularly odd-looking one you could be naming the next cicada after that very loud mother-in-law that asks overly-personal questions every Christmas…. just a suggestion. 😉

9 comments

  1. Love it! Science as Greek tragedy. Fun stuff,, CSIRO!

  2. Hi! My name is Derek, and I think I have fixed my Cicada Problem, and believe my simple idea, has broken the Cicada Life Cycle, and eliminated the noisy pest over the last four years,
    I have a beautiful Spanish Oak/Pin Oak in my backyard, which would be infested with these horrible creatures, who mated, hatched into grubs, and then dropped to the lawn, and burrowed into the ground, leaving a dozen or more unsightly holes about 10-15mm in diameter. Four years ago, I made a skirt from shade cloth cut approx: 1 metre wide, then wrapped it around the trunk of the tree, with the hem about 2 metres high, and using a length of rope, I created a sort of belt at the top of the shade cloth. I then added some nails at the bottom of the skirt, so that the shade cloth would sit away from the trunk of the tree, creating an inverted funnel shaped trap. The cicadas hatch in the ground, and climb up the tree, and become trapped at the top of the skirt. Each morning, using a flat piece of timber, I would squash them through the shade cloth………after that first year of entrapment! You guessed it, no more Cicadas! No more unsightly holes in the ground, and “No More Shrieking Bugs!!”

    1. Perhaps you should receive the same treatment

  3. Mothers-in-law read blogs too you know

  4. The University of Florida’s online “Book of Insect Records” ( https://entnemdept.ifas.ufl.edu/walker/ufbir/chapters/chapter_24.shtml ) gives a very detailed study of insect loudness with specific recorded values up to 108.9 dB (Max. SPL for single specimen at 50 cm from the meter.) Regretably, no Australian cicadas are listed.

    M.S. Moulds’ field guide, “Australian Cicadas” cites the Double Drummer (Thopha saccata) as the loudest cicada at “almost 120 dB at close range.”

    CSIRO’s anechoic chamber would be the ideal facility to prove the world’s loudest insect is our renowned Double Drummer. Go for Decibel Gold !

  5. Could you please caption the second lot of images? What’s that beautiful grey one?

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