Zemeros flegyas has purplish brown upperwings with reddish-brown stripes. The front and hindwings are traversed by four series of small white dots, each freckled by a black spot. There are black and white cilia. The underside of the wings is bright brown with a paler streak, there are also white spots that are bordered by black but larger and more prominent. The antenna is brown with a white ring, the head, chest and back are brown.
Larva: The larvae of Zemeros flegyas are ovate and very flattened. Each segment of the body is rounded, giving it a bumpy appearance. It is pale green in all instars, and is covered in short setae. The length of the caterpillar reaches 19 mm.
Pupa: Zemeros flegyas pupae is fusiform, bright greenish yellow with emerald green stripes, smooth surface. The pupa is about 14 – 18 mm long.