Larvae of three species of Proteoteras (P. willingana (Kearfott), P. crescentana Kearfott, and P. aesculana Riley) attack shoots of Manitoba maple (Acer negundo L.) in the Canadian prairies. Larvae of P. willingana and P. crescentana have been confused because both cause gall formations on Manitoba maple and both lack the anal fork that is present in P. aesculana. This paper describes the ultimate larval instar and pupa of P. crescentana. Keys are presented to separate mature larvae, pupae, and adults of the three species.