Diptera.info :: Identification queries :: Diptera (adults)
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 Gonia ornata (Tachinidae)
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| Karol Ox |
Posted on 15-06-2014 17:48
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 Member Location: Slovakia Posts: 1317 Joined: 25.01.11 |
Hello. It is a Gonia? Found: 27.4.2014, Slovakia-Kosice, 200m a.s.l. Thank you for your help. Regards, Karol. Karol Ox attached the following image:  [191.66Kb] Edited by Karol Ox on 23-06-2014 13:56 |
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| Karol Ox |
Posted on 15-06-2014 17:48
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Member Location: Slovakia Posts: 1317 Joined: 25.01.11 |
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Karol Ox attached the following image:  [195.85Kb] |
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| ValerioW |
Posted on 18-06-2014 23:10
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 Member Location: Padova - Italy Posts: 982 Joined: 01.06.12 |
 Considering the median dark band my end is G. vacua |
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| ChrisR |
Posted on 19-06-2014 09:00
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 Administrator Location: Reading, England Posts: 7699 Joined: 12.07.04 |
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.
Manager of the UK Species Inventory in the Angela Marmont Centre for UK Biodiversity at the Natural History Museum, London. |
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| ValerioW |
Posted on 19-06-2014 09:22
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Member Location: Padova - Italy Posts: 982 Joined: 01.06.12 |
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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| ChrisR |
Posted on 19-06-2014 09:34
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Administrator Location: Reading, England Posts: 7699 Joined: 12.07.04 |
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 
Manager of the UK Species Inventory in the Angela Marmont Centre for UK Biodiversity at the Natural History Museum, London. |
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| Karol Ox |
Posted on 20-06-2014 14:21
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Member Location: Slovakia Posts: 1317 Joined: 25.01.11 |
Chris, Valerio thank you |
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| Zeegers |
Posted on 22-06-2014 20:26
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Member Location: Soest, NL Posts: 18531 Joined: 21.07.04 |
IN vacua, the black vitta is muich smaller. This is simply Gonia ornata. Theo |
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| Karol Ox |
Posted on 23-06-2014 13:56
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Member Location: Slovakia Posts: 1317 Joined: 25.01.11 |
Zeegers wrote: IN vacua, the black vitta is muich smaller. This is simply Gonia ornata. Theo Thank you very much |
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| ValerioW |
Posted on 23-06-2014 15:00
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Member Location: Padova - Italy Posts: 982 Joined: 01.06.12 |
Zeegers wrote: IN vacua, the black vitta is muich smaller. This is simply Gonia ornata. Theo 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 ValerioW attached the following image:  [18.72Kb] Edited by ValerioW on 23-06-2014 15:27 |
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| ValerioW |
Posted on 23-06-2014 15:20
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Member Location: Padova - Italy Posts: 982 Joined: 01.06.12 |
I know you may think I'm goin insane to contradict you  , 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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| ValerioW |
Posted on 23-06-2014 15:24
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Member Location: Padova - Italy Posts: 982 Joined: 01.06.12 |
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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| Zeegers |
Posted on 27-06-2014 07:55
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Member Location: Soest, NL Posts: 18531 Joined: 21.07.04 |
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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| ValerioW |
Posted on 27-06-2014 08:21
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Member Location: Padova - Italy Posts: 982 Joined: 01.06.12 |
Thanks 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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| Zeegers |
Posted on 27-06-2014 09:42
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Member Location: Soest, NL Posts: 18531 Joined: 21.07.04 |
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 |
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but don't see the image in the post.