The life history of Dynastor macrosiris Westwood (Lepidoptera: Nymphalidae: Brassolinae) is described from material reared on Aechmea nudicaulis Linnaeus in the family Bromeliaceae. The huge egg is 3.50 mm in diameter, ribbed vertically, and white when first deposited, later turning to pink with larval development. There are five larval instars. All are characterized by fleshy spines on the dorsal centrum, short on head and caudal segments and longest in the center. The bodies are striped lengthwise in alternating whitish green and darker green lines, with several dorsal maroon blotches. A bifid tail is present. The head has four knobby spines on each side. The pupae is shaded beige and chocolate brown, and strikingly resembles a lizard or snake head. The complete life cycle of this rare and very unusual bassoline takes 70 days (for a male) at ambient temperatures in Trinidad (12 days in the egg stage, 42 days in five larval instars, and 16 days as a pupa).
