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Hello.
It is a Gonia? Found: 27.4.2014, Slovakia-Kosice, 200m a.s.l. Thank you for your help.
Regards, Karol.

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|t Considering the median dark band my end is G. vacua

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Definitely Gonia but I'd need a specimen to be sure of species - the dusting, face colour and width of central band are all variable abd need close examination.

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Ok! Using Cerretti‘s work :abdomen colour + head/abdomen pruinosity colour + abdomen median dark line shape (thickness and pointed end on t5 ) + face corner hairs I went quite straight to vacua

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It definitely could be vacua but I just know people have warned about identifying Gonia from photos because they often don't represent the features adequately :)

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Chris, Valerio thank you :)

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IN vacua, the black vitta is muich smaller.

This is simply Gonia ornata.


Theo

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Thank you very much |t

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Wait. G. vacua is differentiated from others like capitata, bimaculata and ornata , because its median dark stripe shrinks progressively at T5, till it ends, while the others got a stripe that enlarges from T5 (sometimes even from T4). I mean, is quite clear that here that stripe isn't enlarging in T5, instead is shrinking, isn't it?

I add a digitalized scheme of this dark median stripe on T5

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I know you may think I'm goin insane to contradict you :D, Theo, but this cannot be ornata, or at least cannot be ornata from its classic descriptions (with median dark stripe enlarging from T5)

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Here's an example of ornata taken from photogallery. Here is easy to notice the so called "enlarging dark stripe" :)

http://www.diptera.info/photogallery.php?photo_id=7491

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In vacua, the light dusting on tergites 3 and 4 is hardly visible, in ornata it is conspicuous. This made (and makes) me believe this is ornata.
I agree that the black vitta is usually broader in ornata. However, this feature is pretty variable. I have seen 100's of ornata. 10 % of them are even totally black !
You can also observe a kind of dark hind margin of tergite, which I have never seen in vacua (admitted: not seen 100's of those).
Finally, vacua is pretty rare and ornata is pretty common. A Gonia should be pretty clear vacua before I'd make that call.

So, all in all, one feature indicates vacua and the others ornata, which makes me believe this is ornata.

Theo

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|tThanks for the explanation. Probably it's time for tachinid flies description to be updated, because the "dark median stripe shrinkage" is really "trap door" (and no way to escape from it).

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Individual variations, one might say aberrations, can be enormous in Tachinidae. To find flies with left and right with different number of bristles is quite common.
Some variations are known to be common in some species, ie. for instance Oswaldia muscaria with an O. eggeri-like number of bristles on the thorax. With a simple key, one definitely goes wrong, while put together in a box the difference is more than obvious to the naked eye.
Extreme examples are in my experience a Nowickia ferox with a very long petiole in its wing venation. Another source of aberration are intersexes (not that rare at all !)
So, message: don't bother too much about one individual aberration. It is annoying, but they occur.

If you have two specimen with the same aberration, that is another matter.

In Gonia, in my experience the presence of light pruinescense and the extension of this, is quite stable feature. Therefore, I rely on this more than on the shape of reddish sidemarkings or black vitta.

And in the end, I am satisfied with 95 % reliable identification from pictures. Really 100 % is not possible without specimen on your desk.


Theo