Details of the egg, larval, and pupal morphology of Adeloneivaia fallax (Boisduval) (Lepidoptera: Saturniidae) are described and illustrated and compared with other species of Saturniidae, more specifically with other Ceratocampinae. Egg ultrastructure is described for the first time in Ceratocampinae; larval chaetotaxy is documented for the first time in Adeloneivaia; and few pupal characters are evaluated for their potential phylogenetic use. Biological and behavioral aspects of captive rearing are discussed, and larval host plant records for A. fallax are provided.