Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on,
While these again have greater still, and greater still, and so on.
Last Saturday, walking in the Yorkshire Dales with friends, I spotted my first sexton beetle:
It was only when I returned home and examined the photograph I had taken more closely that I noticed the other creature perched on the beetle's head (view larger image): some sort of mite or louse is my guess, perhaps picked up from the corpse of a creature the beetle had just buried.
Insects living on top of other insects. Who could doubt the grandeur in Darwin's view of life?