The first instar larva of a species of the Australian endemic genus Aenigmetopia Malloch is described for the first time, along with the first instar larvae of three other Australian species representing the genera Amobia Robineau-Desvoidy and Protomiltogramma Townsend. Larval morphology was analysed using a combination of light microscopy, confocal laser scanning microscopy and scanning electron microscopy. The following morphological structures are documented: pseudocephalon, antennal complex, maxillary palpus, facial mask, modifications of thoracic and abdominal segments, anal region, spiracular field, posterior spiracles and details of the cephaloskeleton. Substantial morphological differences are observed between the three genera, most notably in the labrum and mouthhooks of the cephaloskeleton, sensory organs of the pseudocephalon, spinulation, sculpture of the integument and form of the spiracular field. The first instar larval morphology of Aenigmetopia amissa Johnston, Wallman, Szpila & Pape corroborates the close phylogenetic affinity of Aenigmetopia Malloch with Metopia Meigen, inferred from recent molecular analysis. The larval morphology of Amobia auriceps (Baranov), Protomiltogramma cincta Townsend and Protomiltogramma plebeia Malloch is mostly congruent with the morphology of Palaearctic representatives of both genera.