Calycopis isobeon, commonly known as the Dusky-blue Groundstreak, is a small butterfly in the family Lycaenidae. It belongs to the group of hairstreaks known as groundstreaks, which are often subtle in colour but richly patterned on the underside. The upper side of the wings is typically brown, sometimes with a faint bluish sheen near the base. The underside is more distinctive, showing soft gray to bluish tones with fine lines and delicate markings, along with small tail-like projections on the hindwings. Near these tails are tiny eyespots that can help misdirect predators toward the less vital wing edges. This species is found in Mexico and Central America, inhabiting forest edges, scrub, and open areas. It is often seen perching low on vegetation or near the ground, frequently with wings closed, making use of its cryptic underside for camouflage.