The fruits and seeds of ciprés de la cordillera [Austrocedru s chilensis (D. Don) Fl. et Bout.] are frequently attacked by a microlepidoptera larvae whose damage percentage become s important depending on the fructification intensity of the host. The agent's annual development was studied, in the field and lab, through periodical fruit collection. The family to which it belongs, its biological cycle, time of attack and natural controls, were determined during the 1994-95 and 1995-96 damage evaluation periods. Since the bio-ecologycal aspects of the species are unknown, the work contributes with information on its biology as it is one of the most important insect species affecting natural dispersion of ciprés: a species of great significance in the Patagonian Ande s ecosystems.