The Stilt-Legged Flies - Micropezidae

Flies.

True flies, to be specific; the two-winged members of the order Diptera  - I feel like we've neglected them a little*. They are, after all, the second largest order of insects in terms of described species, and - as I'm currently trying to come up with a rough key to the families of flies in Zambia, I'm currently painfully aware of just how diverse they are.

Based on recorded distributions of the 159 or so fly families globally (some are sometimes subsumed, there should be some 100 - not roughly, that is actually the number - families of flies present in Zambia.

Note that that isn't 100 'types' of flies, or 100 'species' of flies, but 100 families of true flies; some of which contain hundreds of known species in the region, some of which are only separable by dissection of the genitalia (ow) - and this may only represent a fraction of the actual diversity of this (understudied) country.

As you might imagine, these can be a nightmare to identify - even in groups where species are physically very different, because many taxonomists of history were so concerned with minute differences of genitalia that they neglected to mention the massive external differences between related genera and species (this is essentially why we have voucher specimens and museums: so that authors who think one feature is the most important don't end up making a taxonomic group completely unworkable. It doesn't always work).

Many of these 100 families, however, have only a few species in the region: while there are several dozen species further North in the continent, Southern Africa hosts only six species of the family Micropezidae, and records indicate that Zambia hosts even fewer.

To interrupt this long block of text, here's one of them: 

Mimegralla, probably Mimegralla fuelleborni (Enderlein, 1922, photographed on a farm outside of Mazabuka. 

You'd think with so few species, we'd know just what they do with their daily lives.

We do know a little, but the trouble with these flies is that they are fairly small and inconspicuous, and rarely - if ever - common, so that even with only six (known) species in the entirely of Africa below the Zambezi, the most insightful observation that the-usually-helpful Barraclough** made into their life histories was that their curious white fore-limbs could to be some sort of imitation of ichneumon wasps. Quite how it would benefit the fly to imitate a wasp which cannot sting remains unclear.

As to the rest? Well, one Indian species (Mimegralla coerulifrons (Macquart, 1843)) is a pest in commercial ginger and turmeric farming, and as a result has been quite well studied, and adults have been variously stated to be predatory (which, although this particular species location and behaviour suggested that it was there for the aphids, is doubtful applied across the entire family), and the suggestion that larvae are saprophagous (same link as the last, even though I should chase it the source, I know).

And if we throw in anecdotal claims, it gets even more confusing.

So let's not. Let's just enjoy them.

Here's another, this time Erythromyiella rufa (Hennig, 1935) from Lusaka South:





And, well, at some point I must learn how to write some sort of conclusion to these things instead of just trailing off..










*Not entirely - we have covered a few before - a long, long, long time ago: a rather unusual 'flesh fly' -  Dolichotachina caudata - which probably, like its closest well-studied relatives, acts as a cuckoo to burrow-nesting wasps; the extraorinary long-horned cranefly Megistocera filipes, never previously recorded in Zambia; the bizarre Stalk-eyed Diasemopsis meigenii, four hoverflies all trying - with varying success, to convince us that they are wasps or bees (Senaspis haemorrhoa, Helophilus pendulus, Episyrphus balteatus and Metadon inermis), and the inexplicably named 'centurion' Chloromyia formosa. 


**If you are interested in Micropezidae south of the Zambezi and Kunene rivers (i.e. Zimbabwe, Botswana, South Africa, Southern Mozambique and probably-not-Namibia-because-they-are-mostly-forest-associated, do download the Barraclough (1996) paper, as it contains descriptions of all 6 regional species, and a decent key. I suspect that in the Northern parts of Zambia, Mozambique and Malawi, we get a few more recently-described (or undescribed) species - Tanzania certainly does - but for Southern Africa, this seems to be your lot.