This essay argues that the figure of the firefly sheds light on an environmental poetics that expands our understanding of how literature represented slavery in the Romantic period. Focusing on Edward Rushton's West-Indian Eclogues (1787) and Charlotte Smith's "To the Fire-fly of Jamaica, seen in a Collection" (1804), I trace how the firefly exposes the intersection of slavery and natural history, and thwarts the familiar abolitionist impulses to metaphorize, sympathize, and sentimentalize. Flickering on and off, the firefly ultimately registers the failure of a figure to capture and a poetics of intermittence and parataxis that resurfaces in contemporary Black ecopoetry.