DIPTERA > BRACHYCERA | Higher Diptera

MUSCOMORPHA > ASCHIZA > Platypezoidea > Platypezidae (34 species)

(subfamilies: Callomyiinae, Microsaniinae and Platypezinae)

Closely related to Syrphidae hoverflies that are taxonomically classified in a separate superfamily together with the Pipunculidae big-headed flies, the Platypezoidea comprises two families that are commonly known as flat-footed flies; Opetiidae with just a single British species and Platypezidae, as featured here, with 34 species. The Phoridae scuttleflies are also members of this particular group of species, as are the Lonchopteridae spear-winged flies in some classification systems, although the British list places them in their own superfamily. However, regardless of the actual classification of these species, they are all in the MUSCOMORPHA > ASCHIZA subdivision where, as previously explained on the thumbnails page, the emerging adults do not need to force an exit from their pupal case with a ptilinum and, as such, do not have the inverted U-shaped suture above the antennae. 

Platypezid flies are characterised by having a broad head with holoptic eyes in the male, erect antennae with a terminal arista, a humped thorax, acrostichal bristles either as a single median row or absent, broad wings with a well-developed anal cell, and hind legs that are more or less enlarged and often with broadened tarsi, which are particularly broad and somewhat flattened in the females of subfamily Platypezinae, hence their common name of Flat-footed Flies. While the males of most species, and some females, are mainly dark-coloured, in certain genera there's sexual dimorphism with the females often being more brightly coloured with distinctive brown, grey, silver, yellow or orange markings.

As noted, the latest British list includes 34 species in three subfamilies; Callomyiinae with 16 species in 3 genera Agathomyia (11), Callomyia (4) and Platypezina (1); Microsaniinae with just 5 species in the genus Microsania; and Platypezinae with 13 species in 7 genera Bolopus (1), Lindneromyia (1), Paraplatypeza (2), Platypeza (4), Polyporivora (2), Protoclythia (2) and Seri (1)   

Apart from the five Microsania species, commonly referred to as 'smoke flies' due to their attraction for swarming around bonfires and burning wood, all of the typical flat-footed platypexids are believed to be fungal feeders with their larvae developing in living fungal tissue. Each species seems to have a specific preference, such as gill fungi or various types of polypore. Accordingly, the adults of many species will be found in woodland areas as most of this fungus is saproxylic. Here, in the vicinity of their fungal host, you might be able to find both the males and females of some species on the leaves of broadleaved trees, especially hazel, horse-chestnut and sycamore, either resting or more likely running around in jerky movements feeding on honeydue. The females may also be found ovipositing on fungus, typically on the underside of the cap between the gills or on the pore surface of polypores so it's always worthwhile looking. This lifestyle of course means that the best time of the year for finding platypezids is in the autumn with the most productive months being September and October, although there are a couple of species that may still be active into November.

At the time of writing, there are less than a thousand individual records nationwide with only ten species having more than fifty confirmed sightings. The most frequently recorded species is Protoclythia modesta, followed by Callomyia amoena, Paraplatypeza atra, Agathomyia unicolor, Agathomyia antennata and then another of the species that I've been fortunate to find, Protoclythia rufa, which has only been recorded a handful of times in the south and, up to now, never from Dorset.

Detailed keys enable identification to subfamily via wing venation; Microsaniinae where the main veins run straight through to the wing margin without any cross-veins in the apical half; Callomyiinae where a posterior cross-vein is present and, apart from Platypezina connexa, vein M does not fork; and Platypezinaea where again the posterior cross- vein is present and vein M does have a definite fork. In Platypezinae the wing venation is also important in determining the correct genus, either with reference to the shape of the anal cell or the relative position of the dm-cu cross-vein to the wing margin. Consequently, a good clean, preferably non-reflective photo of the wings is vital. Identification to species is a bit more involved, particularly with certain genera, and may include specific details regarding facial bristles and/or the general form and make-up of the legs, such as the respective length of the first hind tarsomere which is particularly important when trying to separate the two Protoclythia species from Platypeza - elongated in the former and chunkier, more compact in the latter. The females of quite a number of species have characteristic thoracic and/or abdominal markings so, obviously, it's again important that as much detail as possible is captured when photographing these species for subsequent identification.  

Although I only photographed my first flat-footed fly at the beginning of October 24, which I have to admit at the time was a lucky find rather than a targeted species, I decided that it was a family that needed to be looked at in more detail. I like the challenge of small species especially when there is a reasonable chance of identifying them from photos and, when I subsequently learned that very few people actually photographed or recorded platypezids, I knew that they were going to be another of my 'small world discoveries' that I would enjoy in the future. Unfortunately, I'm going to have to wait until next autumn to try to find some new species, but to have had three successful attempts after that first chance encounter when I was able to find a further four species, I now have a pretty good understanding of where I'm likely to find them.

Looking forward, and to provide as much room as possible for future photos and brief descriptions of the species that I've been able to find, I've extended this particular family onto three pages so that the two primary subfamilies Callomyiinae and Platypezinae each have their own separate space.

Please use the forward 'next page' (>) button above to move on to the Callomyiinae subfamily.

Oct.24