The above image is a picture of a Roman mosaic depicting memento mori. The mosaic was created in the 1st Century. Memento mori is a reminder of mortality. The words are meminī ‘to remember, to bear in mind’ and mori “to die”,[1} meaning “remember that you must die”. Ecclesiasticus 7:40:
“In all your works, remember your very end, and so you will not sin, unto eternity.”
The death’s-head is an image or reminder of our “very end.” Beneath death’s head we see a butterfly, representing the ephemerality of the living soul. Carl Jung shows the association between the etymology of the word soul and the butterfly.
“The German word Seele [soul] is closely related, via the Gothic form saiwalo, which means ‘quick-moving,’ ‘changeful of hue,’ ‘twinkling,’ something like a butterfly.” 
The butterfly as image of the soul is in stark contrast to death’s head. Both sit above the wheel of fortune. It is said that the wheel of fortune “can make the rich (symbolized by the purple cloth on the left) poor and the poor (symbolized by the goatskin at right) rich.” Contemplating the ephemeral of life as represented in the image, we realize that both states are very precarious, with death never far and life hanging by a thread: when it breaks, the soul (symbolized by the butterfly) flies off. And thus are all made equal” 
- The Archetypes and The Collective Unconscious (Collected Works of C.G. Jung Vol.9 Part 1) para. 55
- Naples National Archaeological Museum