05 August 2005

Cicada ruminations


I found this skin of a cicada nymph on a signpost yesterday. Such empty skins left behind by insect nymphs have always intrigued me. The skins usually preserve the external organization of the larvae—from the minute hairs to the bulging transparent eyes—perfectly.

For several years I have kept a cicada skin similar to this one on my desk. Sometimes I cannot help but wonder whether, if I touched it gently, it would start crawling among the clutter on my desk. But a large slit on its back gives its secret away. This is the slit through which life escaped, carried away by the adult insect in its new cells. What is left is an organization of dead cells. If we could scrutinize the insides of the remaining cells we would see that the molecular organization that was once responsible for life, the primary structure of the organism, is now destroyed, although the various organs and other structures formed by the cells, the secondary structure, and the overall organization of the organism, the tertiary structure, are still mostly intact, at least in their external appearances.

The adult insect that came out of the skin on the post was probably one of the annual species the nymphs of which emerge from the soil every summer. If it hasn't been eaten by a bird yet, it is probably somewhere on a tree now trying to ensure that at least some of its genes will live on.


1. These ideas are in part from a paper I published many years ago: Örstan, A. 1990. How to define life: a hierarchical approach. Perspectives in Biology and Medicine, 33:391-401.

5 comments:

Spinning Girl said...

very, very cool.
bzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz...

little kernel said...

I'm a total insect buff, thanks for sharing this!!

deniz said...

another lay person's question, and this time it's really really "lay": how come when an insect or snake sheds its skin, the skin remains intact and doesn't decompose at all? If we could shed our skins, why wouldn't they stay intact? Is it just a mammal/reptile difference; what do their skins have/lack that ours don't/do?

AYDIN ÖRSTAN said...

Skins of insects & snakes do decompose, but it may take a while, because they dry out quickly after they are shed. Microorganisms don't grow readily on dry organic matter. Actually, if you look at the picture of the cicada carefully you will see that there was something growing on it, probably some fungus.

tenodera said...

This, judging by the robust builg of this shell, is probably of tibicen species. It's almost impossible to identify a species using a cicada shell...Anyway, this is indeed an annual. There are several genuses of annual cicada- tibicen, diceroprocta, okanagana, and platypedia. Some people asre even lucky enough to find a neocicada heiroglyphica cicada, which is svery beautiful. type it in at google image search and you'll see what i mean!