none The larva, pupa, cocoon, and adult of Ithutomus formosus Butler are described and illustrated. The larva webs together the terminal leaves of Drimys winteri J. R. & G. Forster, thereby creating a nest inside of which it skeletonizes the foliage. A single generation was observed, with pupation occurring during late summer (February) within a dark brown, loosely woven cocoon inside the leaf nest. Adults emerge in March. The immature stages (possibly pupa) of I. formosus are parasitized by three species of Ichneumonidae, Anaepis varipes (Porter), Campoctonus species, and Diadegma species and one species of Braconidae, Bracon species.