Beris morrisii
Beris morrisii, the yellow-legged black legionnaire, is a European species of soldier fly. Description
Length 6.0 to 7.0 mm with narrow frons and face and antennae that are inserted well below the middle of the head profile. 3rd segment of antennae equal to or slightly longer than basal segments together. Face with light-colored pubescence. Yellow thoracic pile and yellow halteres. Uniformly yellow legs except for dark tarsi (basitarsi often yellow in the females). Wings hyaline or slightly yellowish, with distinct brown pterostigma. Outer margin of epandrium pubescent. Biology
The Flight period is May to September.Beris morrisi Larvae have been found  in tunnels of Cheilosia canicularis Panzer (Syrphidae) in rhizomes of Petasites. References

Stratiomyidae
Diptera of Europe
Insects described in 1841
Taxa named by James Charles Dale