There are two subspecies of
Euphyes dukesi: the nominate subspecies discovered in 1922, and a swamp-dwelling Florida subspecies discovered in 1995. The divergence of two subspecies may have occurred due to isolation of Florida and other populations during the
Wisconsinian glaciation or an earlier glacier event, with boreal forests acting as barriers.
E. d. calhouni is named after John Calhoun, who studied its ecology and recognized its distinctiveness, and Shuey proposed the common name Florida swamp skipper to emphasize its endemic range and habitat, but which has also been proposed for the species
Euphyes berryi. Distinguishing characteristics between the subspecies: • The ground color of
E. d. calhouni is darker, nearing black, compared to the dark brown ground color of
E. d. dukesi, which contrasts with a black stigma in males. • Dorsal wings of
E. d. calhouni have overscaling of olive-brown hairs, while
E. d. dukesi have overscaling of orange-brown hairs. • On the ventral forewing of
E. d. calhouni, overscaling is olive brown, while on
E. d. dukesi overscaling is heavier and is orange brown, in strong contrast with the ground color. • On the ventral hindwing of
E. d. calhouni, the yellow dash between veins M1 and M2 is diffuse and often does not reach the edge of the wing, and there is usually no yellow dash between veins Cu2 and 2A. On
E. d. dukesi, both yellow dashes are typically heavily scaled and extend boldly to the edge of the wing in fresh specimens. • Wing fringes of
E. d. calhouni are mostly dark and match the dorsal ground color, except a lightening in the anal region of the hindwing. In
E. d. dukesi the fringes are lighter than the ground color. ==Conservation status==