I remember spotting this large fly as it was quite preoccupied dining on another, smaller fly. The femora of this robberfly are black on the anterior (towards the head) surface and orange on the posterior (towards the rear) surface. Length 10-13mm.
Like all robberflies, it predates on other insects, mainly smaller flies, sucking them dry with their needle proboscis, which can take up to thirty minutes. The larvae feed on dead vegetation.
It flies June to October, and is found in woodland, grassland, gardens, sandy heaths and coastal areas. Britain’s most commonest robberfly, found in scattered populations throughout.
August 2015, front garden, Staffordshire. © Pete Hillman 2015. Nikon D3200, with Sigma 105mm macro lens.