fg-taxon #53 (Borgmeiermyia sp.)
This is one of a pair of very similar taxa (the other is fg-taxon #52) – very small in size (3-5mm), with black body, orange legs and plain wings. This taxon has a shorter antennal segment 3 and a little more dusting.
EDIT (Monty Wood 26/9/2010): This is a Borgmeiermyia sp. – but not one of the multi-fissicorn species.