Cheilosia

The largest genus to be found in the UK, with a total of 38 species, and one of the hardest to identify. Most species are essentially medium sized black flies, meaning that small differences in morphology, hairiness and colouration of body parts such as antennae and legs are crucial in reaching an identification. Without examination under a hand lens, many individuals will go unidentified, although with experience some species become recognisable in the field (I'm still struggling to reach this stage!) Rather than listing all 38 species in a single list as I've done for the other genera, I've split the Cheilosia into sections based on the key in Stubbs and Falk, which helps to make the number of species a bit more manageable. These should be run through in order, jumping to a later segment without checking the earlier ones may lead to the wrong species.

A: Wings with dark clouding in the centre, one bumblebee mimicking species

B: Face with erect projecting hairs - I often struggle to see this - will try and get a decent photo of it!

C: Front tarsus with an orange middle - sections 2,3,4 standing out against the black 1st and 5th sections. Legs otherwise black.

D: Eyes bare and legs entirely black.

E: Eyes bare and legs partly yellow, including basal quarter or more of the tibiae.

F:Eyes hairy and legs entire black

G: Eyes hairy, hind tibia entirely pale, or with only an indistinct dark ring. Scutellum often lacking marginal bristles

H: Eyes hairy, hind tibia dark or with a dark ring. Scutellum has bristles. Sternites 2-4 obviously dusted.

I: As above but sternites 2-4 glossy, antennae dark and hind tibiae at least half black

J: As above but with antennae orange, or if dark then hind tibiae less than half black.

Group A: illustrata and caerulescens

Cheilosia illustrata, the only bumblebee mimicking Cheilosia, widespread and common

Cheilosia caerulescens, recent addition to the UK list, the dark clouds in the wings distinguish it from other similar species. Also has a distinctive facial profile.

Group B: Species with erect projecting hairs on the face

Cheilosia griseiventris

Cheilosia latifrons

Cheilosia lasiops

Cheilosia barbata

Cheilosia variabilis

Cheilosia vulpina

Group C: mutabilis, albitarsis, ranunculi

Group D: antiqua, impressa, sahlbergi, vicina, nigripes, pubera, ahenea

Group E: soror, pagana, scutellata, longula

Group F: impressa

Group G: uviformis, grossa, chrysocoma, albipilis, nebulosa, bergenstammi, fraterna

Group H: velutina, proxima

Group I: semifasciata, carbonaria, cynocephala, vernalis

Group J: bergenstammi, urbana, psilophthalma