DIPTERA > BRACHYCERA | Higher Diptera

EREMONEURA > Empidoidea > Hybotidae (182 species)

(subfamilies: currently Hybotinae, Ocydromiinae and Tachydromiinae - previously including Bicellariinae, Oedaleinae and Trichininae)

Formally part of the Empididae, which was then a very large family, these species together with their associated subfamilies were separated and placed within the Hybotidae where they retained the common name of dance-flies. They are typically small dark flies that, like the empids, are active predators of various flying insects.

General characters for the family are given as minute to medium-sized (1-6mm) flies; usually dark, but colour variable, yellow to black; eyes relatively large, dichoptic or holoptic; antennae short or with a large third segment and long arista; mouthparts variable; wings clear, or in some cases with markings along the costa and around the radial veins; cell dm absent in Tachydromiinae; legs long, slender and often partially adapted to catching and holding prey; femora of fore legs and/or mid legs swollen in the Tachydromiinae, while in the other subfamilies the femora of the hind legs are swollen.

The wing venation is important for confirming the genus and, if the family is confirmed, there's a good chance that identification can be taken to that level as long as there's a photo showing sufficient detail. Keys are available but, from my limited experience, it's not easy to distinguish these species from photos as they could easily be confused with similar looking species in other closely related families - especially Empididae and Dolichopodidae. Fortunately, there are experts on the UK Diptera FB group that have good knowledge of the ‘Dolis and Empids’ and can often provide some level of id from decent photos even if the actual species can't be confirmed, which is usually the case.

The Bicellaria genus (previously in the Bicellariinae subfamily, but now in Hybotinae > Bicellariini) includes eleven species with Bicellaria vana accounting for just over half the records, and locally more like 95% of all confirmed sightings. However, in respect of the three individuals featured here I was advised to stick with Bicellaria sp.

Hybos culciformis and Hybos femoratus are two of the most frequently observed Hybotidae species. They can be pretty much distinguished by their general appearance; the former with a finely brownish-dusted mesonotum and black legs; the latter with a shining black mesonotum, except for grey-dusted narrow lateral and median stripes, and yellow fore and mid legs. The third member of the genus Hybos grossipes is rarely recorded in comparison and has never been officially sighted locally.

The Platypalpus genus comprises close on 100 species. There are quite a number that are regularly recorded with Platypalpus pallidiventris, P.longiseta and P.calceatus being the most frequent locally. Again though, I was advised to leave both the individuals featured here as Platypalpus sp.  

Tachydromia arrogans is a tiny, seldom seen or recorded species with just a hundred or so confirmed sightings nationwide and with no more than a handful across South Devon, Dorset or South Hampshire. There are fifteen species in the genus and, although I can't comment on the others, this species is quite distinctive.

Updated, Nov.24 (v2)