The Monarch is a common poisonous butterfly that eats poisonous milkweed in its larval stage and lays its eggs on the milkweed plant. Monarchs have a wingspan of 3 3/8 - 4 7/8 inches (8.6 - 12.4 cm). Butterflies are beautiful, flying insects with large scaly wings. Like all insects, they have six jointed legs, 3 body parts, a pair of antennae, compound eyes, and an exoskeleton. The three body parts are the head, thorax (the chest), and abdomen (the tail end). The four wings and the six legs of the butterfly are attached to the thorax. The thorax contains the muscles that make the legs and wings move.