Monarchs are well-known butterflies distinguished by their relatively large size, rusty or orange wings with black veins, and black bodies. The upper surfaces of the wings are rusty or tawny orange with black veins; the wing edges are black with small white spots. The undersides of wings are lighter orange or yellow-brown. The veins are darker on females, and males have a black spot on their hindwings.
The caterpillars are white with black and yellow bands; the head is white with yellow and black markings; a pair of long, black filaments are on the thorax and a shorter pair near the end of the abdomen. The caterpillars are usually are found on milkweeds.