Acaulona & Xanthomelanopsis look very similar to Pennapoda spp. but without the leaf-like antero-dorsal bristles on the hind tibia. The only difficulty with these flies…
An interesting little (3-5mm) phasiine taxon – quite prolific in the peruvian samples. EDIT (Monty Wood, 26/9/2010): This is a group of Acaulona sp.
Recently I had a few chances to go back to the NHM in London and work with the world Diptera collections – it was marvellous!…