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Christmas Bells - Blandfordia nobilis

Monday, December 14, 2009

Cicada Shells

My colleague, David Young, has recently posted about live Cicadas he has seen. I subsequently was in Canberra, and came across a bunch of "shells" of Cicadas, gripping onto the bark of an Ironbark Eucalypt.
These are not dead Cicadas, but rather, the exoskeletons of the Cicadas at the larval stage.Cicadas are reputed to live underground for many years - although some American species are reported to stay in the immature stage for perhaps as long as seventeen years - but who knows for sure?

Hole in ground from which a Cicada has recently emerged.
One could easily poke a finger into the hole.
I do not recommend doing that - for another creature
would surely not waste such potentially valuable "real-estate".
Anyway, having lived a long and peaceful life underground, sucking sap from the roots of their favourite food trees (in Australia, mostly Eucalypts it seems), they emerge, and climb to a suitable vantage point where they hook their legs onto a strong perch, then they begin their final stage of metamorphosis. (Technically, as they are "bugs" (Hemiptera) and do not go through pupation (unlike Butterflies) they are said to have a life cycle of "incomplete metamorphosis". Their larval stages are "nymphs" which basically resemble the adults - just varying in size, until the last stage where wings appear).

The mature Cicada emerges by a process of splitting the back and the head of the shell. Then the head emerges, and it pulls the legs out.
Once free of the constraints of the old shell, the wings start to expand and then they pump the veins inside the wing membrane full of body fluids - or full enough to make the fine structure rigid enough to support the insect in flight.Once that is done it is time for flying, singing and loving.

A brief adult life but a merry one, it seems (hopefully enough to justify the seventeen long years of waiting around underground in the larval stage, anyway).

Here is a study of the "eyes" of a Cicada shell.
And here - the real thing.
Two large eyes, and the three "jewels" are in fact semi-functioning optical points "occelli", which the theory has are able to function underground, to assist the larvae to sense to their environment underground. That's just a theory as far as I am concerned.

You may read a detailed academic study of Cicada biology here.

12 comments:

Gaye from the Hunter said...

Hello Denis,

extremely interesting post!

Every summer I am hoping to stumble upon a cicada emerging from its 'shell', but as yet, I have not seen this spectacle.

I have not found any cicadas or their discarded exoskeletons in my town yard. I always found a few in my rural yard, which had no mature trees to act as food sources for underground larvae. Now I have mature trees, but no Eucalypts. So I wait, and observe. The invertebrate population is vastly different in my town yard to that of my rural yard, which is interesting in itself.

Cheers,
Gaye

Denis Wilson said...

Hi Gaye
I seem to remember lots of Cicadas in suburban Melbourne, around my school when I was a Kid.
The only trees I remember from that place were Plane Trees.
So maybe they do adapt to non-native trees. Not sure.
I have never seen one emerging, but if you are around when they crawl out of their holes, it seems easy to stick it onto a branch and wait and see.
Best of Luck.
Cheers
Denis

Mosura said...

Don't see too many here and the ones I do see are relatively small.

Tho occelli on that last shot look like lit up LEDs.

Denis Wilson said...

Hi Mosura
I am fortunate that Robertson gets very few Cicadas, but they are common down on the sandstone plateau below us.
Those Occelli do look like LEDs - I hadn't drawn that interpretation before, but it is very appropriate.
I might use that comment, in future, if you don't mind.
Nicely observed - Thanks.
Cheers
Denis

Sebastian said...

Nice post Denis. Well done on the investigative photography in particular. This must have taken you a while!

Denis Wilson said...

Thanks Sebastian
I do try to research these stories, especially of subjects out of my normal field - Orchids and birds.
.
This was actually a follow-up to one done a long time ago.
Glad you liked it.
Denis

DBS Young said...

Hi Denis,
Well I caught up with this post at last :)
Fantastic photography!
Cicada have been of great interest to me for over 40 years ( has it been that long!).
I have a video of a cicada emerging firstly from the ground, and then its shell, only to dry its wings and fly away. 2 hours worth of tape that I intend to speed up into a couple of minutes.
I hope to have it posted soon.
You've produced another master work of macro Denis.
Congrats :)
David

Denis Wilson said...

Thanks David for the supportive comments.
I look forward to your video.
I seem not to be patient enough to do the stalking and waiting, etc.
They are fascinating insects, that's for sure.
And so varied and beautiful.
Denis

Jeff said...

Darn! I came out of my house this morning to go to work and saw these incredibly 'weird' creatures on my front step. After doing research, one of these 'creatures' I realized was a cicada emerging from it's exoshell. I was going to take a picture as I had never seen a bug like this ever, but I didn't and I continued on to work. When I got to work I felt guilty for not doing it so I called my wife to take a pic but when she went out she told me it looked different, and the green head portion was gone and just the brownish armour looking part of the bug was left. So I suspect in the period of time it took me to get to work, the cicada emerged and that is its shell left over. Nonetheless, it was neat to see it half way out of the shell.

Denis Wilson said...

Hi Jeff.
Glad you saw one emerging. I never have.
.
I did my story on the many shells I found last summer, and on some adults I had seen.
You were lucky, or rather very observant. There really is no such thing as luck when it comes to nature observation.
Yes, you ought have rushed back inside and got the Camera, and been late to work - but then again, you might have got sacked. So I wouldn't wish that on you.
.
Thanks for sharing your story.
.
By the way, where are you located? Australia or other country? It seems an odd season for Cicadas here, where I am, as we are having frosty nights at present, and I always associate Cicadas with high summer.
So I suspect you are in the Northern Hemisphere.
I would like to know, just to satisfy my curiosity. Cicadas are universal insects. Very primitive, but with a world-wide distribution.
Cheers
Denis

Jeff said...

Hi Denis --
If I had known what I was witnessing at the time, I would have risked being late to take some nice pictures. I have a pretty high end Canon DSLR so they could have been some nice ones (albeit with my skill level I am sure they would not have been up to National Geographic's standards, ha ha). You are correct, I am from the Northern Hemisphere. I am located just outside of Toronto, Ontario Canada. Over the last couple of weeks we have been having some seriously hot weather (40 degrees Celsius with the humidex) and the Cicadas have been singing like crazy in the trees. I love the sounds they make -- always such a great reminder of the summer weather (at least here in Canada). Thanks for your reply!
Jeff

Denis Wilson said...

Hi Jeff.
Canada in high summer, sounds great
Zzzzzzzzzzzzzzzzzzzzzz ZZZZZZZZZZZZ
Zzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzz
SOmething like that, eh?
.
Glad you like it.
Some people are driven nuts by their incessant droning.
.
In another 7 years, expect another hot summer, and a huge hatching of the progeny of this year's breeding program.
.
You will be able to come back and tell us in 7 years if they have had another big year.
.
.
Cheers
Denos