The monotypic genus Latonius Kononova, 1982 (Platygastroidea, Scelionidae), was described from a single female specimen collected in southern Ukraine. It somewhat resembles Trissolcus Ashmead but has a distinctive claval formula. The only species in the genus, Latonius planus Kononova, 1982, is lacking any details regarding biology, sexual dimorphism, intraspecific variability, or distribution. Based on recently collected specimens the present study clarifies the position of Latonius within the Telenominae, provides a comprehensive description accompanied by high quality images, and compares Latonius and Trissolcus. Five molecular markers were amplified, and sequences of L. planus were analyzed using a data set for the molecular phylogeny of Telenominae (Taekul et al. 2014) and a molecular phylogeny of Trissolcus (Talamas et al. 2019). We dissected the metasoma, tarsi, antennae, and ovipositor and performed SEM imaging. The genera Latonius and Ioseppinella Mineo, O’Connor & Ashe, 2010, are treated as junior synonyms of Trissolcus and the type species of Latonius and Ioseppinella are considered to be conspecific (syn. nov.).