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These are very difficult flies to identify without specimens (and sometimes with them, preferably pinned) but to add to Kahis? characters

in Fanniidae- the head is hemispherical ; the arista bare; the middle tibia in the males of some species have a strange structure which may look like deformity. In others bent spurs or thorns point down from the mid coxae. Females are more difficult but there are two strong (big) upper fronto-orbitals outside the row of frontals.

Another pointer- I picked up on the odd pale yellow-brown of the abdomen contrasting with the pale grey thorax. Several common Fannids (eg. F. fuscula) have this appearance (basal only in F. canicularis).

A field character helps . Males swarm beneath tree branches in a zig-zag manner very like that of the house species Fannia canicularis (lesser house fly). When two flies meet they rapidly turn darting apart.

Characters separating the small Muscidae Kahis mentions

Thricops see Kahis comments on the Gallery pic of Thricops semicinereus then note the dorso-ventally (see glossary) flattened abdomen of your pic of cf. Fannia.

Hydrotaea. In males of some species the fore femora are strangely ?deformed? or with odd structure and sometimes the fore tibiae (not mid as in Fannia); females have crossed bristles on the frons and there are two not three sternopleural bristles. Hydrotaea also hover but may be attracted to sweat causing irritation (hence the name Hydrotaea irritans).


Hebecnema. Wings smoky or brownish-black which in the sun can seem very black against a light background.


http://www.entomologieforensique.ch/page2.htm for a good Fannia pic although not the legs. Hydrotaea ignava is less good and again the legs are not seen.

A problem group?

I wrote this some years back.
?The identification of Fanniidae and Muscidae is best accomplished by a judicious use of the following keys, swapping one for another if difficulties are encountered:Fonseca (1965), Seguy (1923) and a series of keys to genera by Collin and Ringdahl.
A good deal depends on the proper interpretation of bristle characters especially of the legs. A most important point is emitted from all current key works... the leg (femur and tibia) flexes in the posterodorsal plane: once this is understood no further problems should be encountered excepting with flies from alcohol traps which lose their characteristic patterns or tessellations. To properly place Fanniidae and Muscidae Unwin (1983) is most useful.?


More keys are available now but the older literature helps sometimes. However this is not identification. It is just getting an answer from a key. In my experience except where a specialist has identified the material most museum specimens even in major institutions are misidentified. Tough call indeed Robert