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.