DIPTERA > BRACHYCERA | Higher Diptera

MUSCOMORPHA > SCHIZOPHORA > Acalypratae > Lauxanioidea > Lauxaniidae (56 species)

(subfamilies: Homoneurinae and Lauxaniinae)

Lauxaniid flies are small (2-7mm), often rather plump, shade-loving species that breed in leaf litter and decaying plant matter. The body colour ranges from pale yellow to orange-yellow, brown, grey, black or combinations thereof; the general appearance either dull or partially lustrous; the abdomen is mostly plain, but in some species, it may be patterned with stripes or small spots; the wings may be clear or yellow-tinged, usually unmarked, although in a few species partially clouded or with spots along the veins. Other family characteristics are given as vibrissae absent; postvertical bristles well-developed and convergent; legs without strong bristles, although the hind tibiae usually have a dorsal preapical bristle (except Minettia longipennis and Sapromyza obsoleta); wings with a continuous costa and distinct, complete subcosta; short, non-extending anal vein; crossvein BM-Cu present; cell cup closed.

The 'British Diptera Checklist' recognises 56 species, which are separated into two subfamilies; Homoneurinae with ten species in a single genus, Homoneura, and Lauxaniinae with forty-six species in twelve genera. I'm not yet at a stage where I could confidently identify many of these beyond the family, let alone to the genus or actual species, so I'm indebted to various experienced members of the UK Diptera FB group that have helped me get a better understanding. It's going to take a while, but at least I can now feature a few different species.

The Calliopum genus includes five species; Calliopum tuberculosum, a common and frequently recorded orangey yellow coloured fly; Calliopum geniculatum and Calliopum elisae, which are black and shiny, the latter being widespread and reasonably common, whereas the former appears to be much scarcer, particularly in the south; and then two other very similar species, Calliopum simillimum and Calliopum aeneum, that have more of a dull bronzy-black appearance. The individual featured below is probably Calliopum simillium based on local records, but Calliopum aeneum is also possible.

Homoneura notata - a small orange-yellow species with no significant markings and tiny black spines on the costa that continue to the end of vein R4+5. It's the most frequently observed Homoneura specis, but still with comparitively few confirmed records of which less than a handful are from Dorset (VC9) or South Hampshire (VC11).

Meiosimyza rorida - a pale orange-yellow species with no significant markings, but with some distinguishing bristles that together with other minor features assist identification. According to the NBN Atlas, it is the most frequently recorded British Lauxaniidae species.

Minettia inusta - a small brownish-orange species with distinctive wing markings.

Minettia longipennis - a rather dumpy black species with slightly orange-tinted wings that have a blackened base; lower face with rounded swellings, and hind tibiae lacking a dorsal preapical bristle.

Minettia fasciata (not yet featured) is the second most recorded species - a distinctive fly with a grey thorax and pale brown abdomen with darker stripes, very similar to Minettia tubidiventris and pretty much inseparable from photos.

The six species within the Sapromyza (sensu stricto) subgenus are distinguished by having a pair of ocellar bristles that originate from within the ocellar triangle, just behind the front ocellus. Although five of these species have been recorded in Dorset at some point, they have mostly been from the west of the county. The most frequent and most likely species locally appears to be Sapromyza sexpunctata, which can be identified by the shiny thorax in conjunction with the back of the head being entirely orange-brown. A clear view of the abdomen reveals six black spots; a feature that is shared with Sapromyza opaca, except that species is much rarer and has a dull thorax.

Two Sapromyza species that have ocellar bristles originating from just behind, rather than from within, the ocellar triangle are placed within the Sapromyosoma subgenus. They can be distinguished by various features, the most useful being whether the acrostichal bristles are in two rows between the rows of dorsocentral bristles as in Sapromyosoma quadripunctata - a distinctive all-orange grassland species with four small abdominal spots - or in four rows as in Sapromyosoma quadricinta, which despite once being recoded in Dorset is now regarded as a very localised species only likely to occur in East Anglia.

Tricholauxania praeusta - a pale orange species with a distinctive darkened cross-vein and slight shading around the wing tips, but also characterised by small bristles on the underside of wing vein R2+3 and a row of tiny black spines on the front femora, neither of which are visible in my photos, so unfortunately the identity can't be confirmed.

Updated Nov.24 (v.4)