Sunday 19 May 2013


Image: James Jordan
Take some earplugs and put them in your ears. Then get some earmuffs and put them over your ears. And then take your hands and cover your ears. You are now ready for a close encounter with a Cicada.

Noise! Loud, rasping, ear-splitting noise the kind of which one usually encounters when the guy next door is practising his washboard playing. That is the major contribution Cicadas have given the world. Noise is what they do to attract a mate and if you annoy one, it's also what they'll do to repel the enemy.

Image: Tony Willis
Chorus Cicada (Amphipsalta zelandica), so named for their synchronised singing
For the Cicada, all is noise in love and war.

There are over 2,500 species of Cicada in the Cicadidae family. It's one of those "every continent except Antarctica" deals, where pretty much every part of the world has at least one species of resident Cicada if not several hundred in the tropics.

Image: petrichor
The Double Drummer (Thopha saccata) is Australia's largest Cicada.
The wings alone are over 6 cm (4in) long!
It's in nice, humid areas that Cicadas reach their biggest size. Most of them are a mere 2 to 5 cm (an inch or two) long, but really big ones can reach more like 10 or 15 cm (4 to 6 in). None of these numbers are small when you're talking about insects! Cicadas are large, robust bugs with huge wings, wide heads and chunky bodies.

Image: Neil Skene
Green Grocer (Cyclochila australasiae) and its three ocelli
They're big enough that between the widely spaced compound eyes you can very clearly see the three ocelli. These are the simple, single lensed eyes that many insects use to tell light from dark. It's thought they are most useful for flying insects in their efforts to maintain stability and not roll around, turn upside down and then immediately lose all track of where they are. This is very important when flies are repeatedly smashing themselves against windows.

Image: Chaval Brasil
Weird face mask thing
Aside from the eyes you can also see that Cicadas have extremely thin, tiny antennae. Below that is what looks like a kind of stripy face-guard, the kind of thing that dominates Optimus Prime's face. It would be nice if all they had was a little mouth behind it. No such luck, I'm afraid.

Cicadas are members of the order Hemiptera, known as true bugs. Or just bugs if, like me, you don't commonly call all sorts of other things "bugs". Hemiptera includes lots of familiar beasties like Shield Bugs, Stink Bugs and Aphids... the kind of thing you'll often see lounging around on your plants drinking up their vital fluids.

Image: SidPix
Cicada drinking a tree
Cicadas are no different. The thing that unites the true bugs, the Hemipteran Membership Card if you will, is their needle-like mouthparts. Almost all true bugs are herbivores who plunge their needle-mouth into plant stems to drink the sap within. Basically they live on cold, watery, vegetable soup, which sounds like prison rations, but they seem to do quite well on it.

Also a bit like prison is all the faeces that gets thrown around. Tree sap is so full of water that Cicadas squirt out the excess with remarkable force, like one of those Super Soaker water guns. It's absolutely appalling behaviour. Don't try it at home! Or, alternatively, ONLY try it at home! It'll get you kicked out of most other places. And if it doesn't, you probably shouldn't be in places like that anyway.

Image: fancycwabs
The tree says "ouch"
So Cicadas drink plant soup through a straw. That's fine. The problem is... they sometimes make mistakes.

VULNERABILITY! It's a dirty word, ain't it? If you're a wolf, it happens when you're demonstrating your submission to the alpha wolf and you're on your back showing off your juicy, throbbing neck. One would like to think that humans don't do that so much, that we show vulnerability in loving relationships, when you feel completely comfortable or when you had a really cool accident.

It's unfortunate then that a comfortable Cicada may well bite you. If you find one relaxing on your arm and staying there for a long time, you might think that you're developing a trusting relationship with it. This illusion will be shattered when it decides that it's been sitting here unmolested for so long that you're probably a tree. Commence exploratory drilling!

Cicadas aren't keen on biting people. It doesn't seem to be a defence mechanism and the proboscis is so long for getting deep into plants that it looks too ungainly for a quick attack. But... you know. Perhaps one day a Cicada will get right through the skin and start slurping up blood and be like "this is really great sap! I love it!" That would be unfortunate for all of us.

Until that fateful development, the main thing a Cicada will do when captured by a predator is scream in outrage. "How DARE you! Do you know who I am?" That's probably a rough translation of the noise they make.

Cicadas don't stridulate like grasshoppers and crickets, stridulation being when one part of the body is rubbed against another, like part of a wing on part of a leg. Instead, they have little structures called tymbals.

It looks like a stripy membrane hidden away in the abdomen. The stripiness comes from the fact that parts of it are very thin while other parts are thickened. Muscles make this structure buckle upward and produce a click, then buckle down and produce another click. You can do a similar thing with a tin!

Male Cicadas have a lot of empty space in their abdomen to make the sound resonate. Not only does this allow some Cicadas to be amongst the loudest of all insects, it also enables them to attract a mate. Which is more to the point. Cicadas don't need adulation from the crowd, they just want a mate. Such wisdom!

Image: Stephen Begin
Try a triple-blade for an extra close shave
Having punctured trees to suck out their sap and effectively urinated all over them, the female now cuts little notches into the tree's twigs and lays her eggs in them. When they hatch, the youngsters fall to the ground, burrow into the earth and start sucking sap from the tree's roots. The poor old tree is attacked from top to bottom! Outrageous!

Cicadas, like all true bugs, belong to the superorder of insects known as Exopterygota. It means that the youngsters aren't maggots, grubs or caterpillars and instead look quite a lot like their parents.

Image: PittCaleb
Cicada nymph
They're called nymphs rather than larvae and have no wings...

Image: Camponotus Vagus
Cicada nymph's claw. Erk!
But Cicada nymphs have large forelegs for burrowing.

Image: Brian1442
Adult emerging from the final moult
They need to moult as they grow, breaking out of their old exoskeleton and developing a new, bigger one. Eventually, the nymphs break out of the ground, climb up a tree and go through their final moult. This is the one where a winged adult since unlike larvae, they don't have a pupal stage in a cocoon.

Image: J-Dill-Photography
Empty skin covered in soil
Famously, some Cicadas emerge in greater numbers than others.

While most Cicadas live for just a few years, there are a few with a lifespan of over a decade. These are the remarkable Periodical Cicadas of the wonderfully named genus Magicicada. There are seven species, all in eastern United States and four of them have a 13 year lifecycle, the other three a 17 year lifecycle. They spend almost the entirety of this time as a nymph underground.

Image: Blue Yonder
When their time comes, the young Cicadas emerge from the earth in their millions. They climb up every available tree trunk to break open their exoskeleton and step out into the world of sunlight, gentle breeze and the other side of the tree they've been munching on this whole time. Their old skins remain in place, clinging to the bark like legions of the undead.

This regular plague is thankfully not as devastating to plant life as it looks like it ought to be. It is however a massive feast for all sorts of hungry animals great and small. It seems that these Cicadas survive by providing a buffet so incredibly satisfying that even after all and sundry have had their fill, there are still millions of adults laying their eggs and laying the groundwork for next time.

Image: cotinis
Magicicada, recently emerged
It's also interesting that these generations are 13 and 17 years long, two, large prime numbers. It's thought that this ensures no predator can align their own lifecycle to take advantage of the regular glut. Alternatively, it may be to prevent hybridisation between different broods. There are some places where the 13 and 17 year cycles overlap but they can only coincide every 221 years!

Oddly enough, there is one who has managed to take full advantage of the Periodical Cicada and align itself to their cycles impeccably. It's a fungus called Massospora cicadina, and its spores are able to lie dormant in the ground for the required 13 or 17 years.

Image: tlindenbaum
Magicicada, ready for action
This stuff grows in the abdomen of the adult, eventually causing some of the rearmost segments to fall off and reveal the despicable cotton wool inside. The Cicada remains alive up its tree but now spores are released from its hind-quarters, infecting yet more of the millions of surrounding Cicadas. It's this second generation fungus that will produce the spores that will lie in wait for a decade.

It's grizzly stuff, but someone has to strike one back for the trees!


TexWisGirl said...

we get the 'every year' variety here. and thank goodness, only the 1 or 2 inch size. my dogs love to catch them and let them buzz in their mouth. goofs! and they eat the ectoskeletons, too. ick!

Unknown said...

Hey, just wanted to say thanks for the incredible blog. I run a life-drawing night with a nude model and projections of weird creatures, and without your blog it would take me many hours to find this many animals to project, so thanks!

I constantly get asked to explain what the hell the thing on the screen is, and because of you I usually can.

I also just read for fun, because holy fuck.

Joseph JG said...

@TexWisGirl: I bet the exoskeletons are the best bit! Crisp and crunchy!

@Rebecca Hartstein: Hahaha! That sounds amazing! It must be pretty weird for people who have to draw a nude human with some crazy creature they might not even have seen before. Great idea!

I'm glad you can find all this useful in some way. That's great!

??? said...

David Attenborough had a very close encounter with a cicada in Life in the Undergrowth. If you listen closely, you can hear the cameraman giggle in the background.

Joseph JG said...

Haha! I never noticed the giggling before, that's hilarious!