Doug Wechsler / Long-legged Fly (Condylostylus sp.) on Common milkweed leaf, Pennsylvania, USA

Premaphotos / Fly (Dolichopus wahlbergi) feeding on an enchytraeid worm, UK

Premaphotos / Thick headed fly (Thecophora atra) on a Fleabane flower, UK

Premaphotos / Common wasp / thick-headed fly (Conops quadrifasciata), male riding on the female's back but not mating, UK

Premaphotos / Long-legged fly (Argyra diaphana) male, UK

Premaphotos / Thick-headed fly (Physocephala rufipes) mating pair, UK

Premaphotos / Thick-headed fly (Myopa testacea) on flower, UK

Premaphotos / Glittering green fly (Poecilobothrus nobilitatus), male grooming his genitals, UK

Premaphotos / Common wasp fly, a thick-headed fly (Conops quadrifasciata) mating pair, UK

Premaphotos / Thick-headed fly (Myopa testacea) mating pair, UK

Nick Upton / Yellow banded conops flies (Conops quadrifasciatus) pair, mating on a scabious flowerhead in a garden, Wiltshire, UK. July.

Nick Upton / Conopid / Thick-headed fly (Myopus pellucida) a parasite of mining bees, sunning on a Honeysuckle leaf in a garden, Wiltshire, UK, April.