The purpose of this application, under Article 75.5 of the ICZN Code, is to conserve current usage of the generic name Trimorus Foerster, 1856 (Hymenoptera, Scelionidae) by setting aside all previous name-bearing types of the type species, Gryon nanno Walker, 1836 and designating a neotype for it. The original description of Gryon nanno is insufficient for recognizing the species, and the name-bearing type is lost. Trimorus is presently considered a large and morphologically variable genus (∼400 species). A type specimen for Gryon nanno that is in accordance with the prevailing usage of Trimorus and can be identified at the species level is needed to maintain nomenclatural stability.