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.