1. A trace is not the thing itself, but a vestige of its passing.
2. Some traces are cut deep and unmistakable—bear tracks in the snow, six pads and the telltale scrape of claws.
3. Other traces are more fleeting, a trail of clues to be deciphered. Are those paws? And if so, what sort of beast was here? You may find yourself wrestling with the uncertainty of what remains.
4. To trace is also to draw or sketch. Create from clues with care, as what you read in(to) the snow can take on a life of its own, rough beasts of twig and ice tapping tattoos on the inside of your skull.
5. A change in the brain as a result of experience is sometimes called a memory trace, which has also been called an engram.
6. When Richard Semon coined the term engram, he was thinking of the Greek goddess Mneme, the muse of memory. He wanted, like so many others, to pin psyche to the brain like a moth to cork.
7. Psyche, who was Cupid’s great love, may be invoked as a metaphor for mind or memory, as if the two are interchangeable. In the famous painting of Psyche and Cupid’s first kiss, a butterfly hovers over Psyche’s head, a symbol of innocence poised before sexual awakening.
8. To trace is not only to track down but also to find or discover, as in for the first time.
9. But memories will not stay pinned in place. They change depending on present tense circumstance—your mood at the moment of remembering or your reasons for looking back, now, which may be the very fork in the road at which you stand, trembling and uncertain.
10. What spoor do Lepidoptera leave in their wake?
Meehan Crist is writer-in-residence in Biological Sciences at Columbia University. Her writing explores the intersection of science, culture, and politics and has appeared in publications such as the New York Times, the Los Angeles Times, the London Review of Books, Nautilus, the Believer, Scientific American, and Science.