It's difficult to say whether this poem about the experience of coming upon a snake in the grass is actually taken from Emily Dickinson's real life. The poet spent much of her time in seclusion in her home in Amherst, Massachusetts and never traveled. Of course, "a boggy acre" could have been close by her home.

It's also easy to imagine a young Emily walking out in a field when she comes upon the "narrow fellow." It is natural for children to explore the outside world and certainly an unforgettable experience would be discovering a snake winding its way through the grass.

Of course, it's equally easy to imagine that this is all the product of Dickinson's fertile imagination. She read voraciously of English literature, and this poem may have been inspired by a scene from some tale or poem she had perused. After all, the narrator is a boy! Dickinson writes,

"Yet when a boy, and barefoot,

I more than once, at noon, 

Have passed, I thought, a whip-lash

Unbraiding in the sun—

English novels, especially those of Jane Austen, the Brontë sisters, Henry Fielding, Charles Dickens and others were often set in the English moors (wetlands). After reading Dickens' Great Expectations, she may have imagined Pip coming across a snake in the moors near the Gargerys' house. The fact that she refers to a boy is evidence enough to prove that the poem might simply be a product of the literary mind of Ms. Emily Dickinson.