Lateral part of the postpronotum, especially in higher Diptera well visible, less so in some groups of lower Diepra (in particular Nematocera). Usually well intergrated with the scutum and often bearing setae (postpronotal setae).
Synonyms: humerus (plural: humeri), humeral callus (plural: humeral calli)
Does someone has a scan of Nartshuk E.P. 2003. Key to families of Diptera (Insecta) of the fauna of Russian and adjacent countries. Proceedings of the Zoological Institute Vol. 294: 1-252 for me?