For terms see Morphology of DipteraThese are slender, medium-sized flies, with long abdomens. The hind femora are  thickened, and bear two rows of spinules on the lower side.
Refer to the Morphology of Diptera for definitions. These are slender, moderate-sized flies with long abdomens. The hind femurs are thickened and bear two rows of spinules on their lower surface.