Pipizella viduata

A small, compact species (8 to 10 mm) with an all-black abdomen. The third segment of the antenna is about 1.5 times as long as wide in the male and about twice as long as wide in the female. It has a row of hairs on the anterior surface of the rear tibia that are only as wide as the tibia itself, which also helps to distinguish it from similar species. 

Pipizella virens has antenna that are longer and narrower (3rd sement: length = 2.5x width)

Found on dry grassland, heathland and disturbed ground. 

May to September, peaking late June and early July. 

Associated with root aphids on several plant species. 

Widespread and fairly common in Britain. 

Quite frequent in Leicestershire and Rutland.