DIPTERA > BRACHYCERA | Higher Diptera

MUSCOMORPHA > SCHIZOPHORA > Calyptratae > Muscoidea > Muscidae (294 species)

(subfamily: Azeliinae)

Azeliinae (59)

The British Diptera Checklist has been adapted to include this subfamily, which may not be recognised by other authors. It includes the following tribes and genera:

Azeliini - Azelia (7), Drymeia (3), Hydrotaea (26), Neohydrotaea (1), Potamia (2), Thricops (16)

Reinwardtiini - Muscina (4)

When I saw that my personal list included only a couple of species from this particular subfamily, I looked more closely at the three larger genera, Azelia, Hydrotaea and Thricops, which jointly comprise nearly fifty species.  I checked all the available records I could find for both Dorset (VC9) and South Hampshire (VC11) and noted how infrequently any of these genera are recorded, which I initially assumed was more to do with reliably determining the species rather than a true reflection of their distribution. However, when I started digging a bit deeper, I quickly became aware that many of these species are not going to be found in my general area.

Anotherpoint to note when looking at distribution data and trying to ascertain the likelihood of seeing species locally is that many records are old, and species that were regularly seen a few years ago, may not be anywhere near as frequent now. That seems to be the case with a number of muscids, particularly with species such as Hydrotaea irritans and Musca domestica mentioned further on. Locally, there are no more than a handful of officially confirmed observations for any of the other Hydrotaea species or, indeed, any of the Azelia. The situation with Thricopsis no better with even the two so-called common species Thricops diaphanus and Thricops semicinereus being very rarely recoded. 

Hydrotaea

With 26 recognised species, Hydrotaea is the third largest muscid genus after Phaonia and Helina but, as noted above, only a relatively small number are likely to be encountered. I can't find much general information, but after photographing the three different individuals featured below, which I think are Hydrotaea dentipes, I had to do some research. The first thing I discovered was that this species is the second most frequently recorded Hydrotaea after Hydrotaea irritans, and by a fair number, so that gave me confidence that I wasn't thinking it was one of the much less common ones. I then had a go at following the 'key' but, not surprisingly, didn't get very far as there are just so many important features, such as leg bristles, that you can't see in these photos. However, working in reverse, I came up with the description of medium sized (6-7.5mm BL) dark-coloured females; thorax and abdomen both with conspicuous pale dusting, which produces distinct presutural longitudinal stripes on the mesonotum; ocellar triangle shining black around the front ocellus; acrostichals well-developed in two complete rows. That looked pretty good, but the males are keyed separately and this is where I started to doubt my assessment as their eyes should be closer together. Looking at the various photos I took, they appear to be separated by about the same distance as the breadth of the third antennal segment. I also think they're hairy, not bare, and if that's the case it could well be Hydrotaea cyrtoneurina rather than Hydrotaea dentipes. Of course they could be two different species, but that's probably unlikely seeing that they were all in the same general location, although not together, so, despite my initial confidence, the following captions are very tentative.

Thricops

As far as I can tell, most of the members of this genus are found further west or north of where I live, with some only occurring in the Scottish Highlands. Only the two species I mentioned above, Thricops diaphanus and Thricops semicinereus, have ever been recorded from either Dorset (VC9) or South Hampshire (VC11). In fact, I think it's pretty unlikely that I'll be able to see any of the other species locally. Statistically, the most frequently observed is the orange- bodied, woodland fly, Thricops diaphanus that superficially resembles Phaonia pallida. These two species are sometimes confused, especially the males, but they can be distinguished by the characteristic fan of posterior bristles on each hind coxa assuming they can be seen, and also the presence of a conspicuous ventral spur towards the tip of the hind tibia. Fortunately, the females are far more obvious as they have a black rather than orange frontal vitta. Thricops semicinereus is an attractive black-legged species with a dark thorax and orange banded abdomen. It's another woodland species that hopefully I'll be able to feature at some point.

Muscina

Relatively large, robust flies characterised by a striped thorax, red tipped scutellum and an upturned M1 vein. Four species are listed, although only three are likely to be seen. The most frequently recorded species is Muscina levida (briefly described below) and, in some areas, Muscina prolapsa although far less common. The other is Muscina stabulans, but there are not that many records. In fact, the situation here is no different locally than with the previous genera as there are virtually no confirmed records of any of these Muscina species.

Muscina levida - a medium-sized (6-8.5mm BL) dark bluish-grey species with distinctive markings, dark legs, wholly black antennae and with the M1 vein only slightly upturned apically narrowing the posterior cell gradually so that the width at the wing margin tip is reduced to about 70% of the widest part of the cell. In Muscina prolapsa the curve is more pronounced, upturning sharply towards R4+5 so that the cell is greatly reduced to around 40% of its maximum width where M1 meets the margin. Another distinguishing feature between these two species is that in Muscina prolapsa the third antennal segment has a red base.

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Updated Oct.24 (v.2)