The adult of the predaceous midge Stilobezzia fiebrigi Kieffer is redescribed and illustrated by using binocular compound microscope, and the pupa is redescribed by using binocular microscope and Scanning Electron Microscope. Immature stages were collected as pupae in mud in flooded soil in Corrientes province, Argentina. Adult and pupae are compared with their similar congener Stilobezzia coquilletti Kieffer.