Abstract The Upper Carboniferous insect Gerarus from Mazon Creek was reinvestigated to assess the affinities of the Geraridae. Specimens were examined using an environmental scanning electron microscope. The evidence, including an inflated clypeus and characters of the wing venation, for placing the family in Paraneoptera (hemipteroids) is equivocal; Gerarus is assigned to the Archaeorthoptera in the stem-group Orthoptera. The presence of leg exites in Gerarus and other Mazon Creek specimens could not be confirmed. Definitive evidence for the origin of insect wings remains to be discovered.