Thread subject: Diptera.info :: Syrphid? --> Scaeva selenitica? Or Scaeva dignota?
Posted by undina-bird on 22-06-2011 23:33
Pls help to ID this hoverfly.
Date: June 17, 2011
Location: 30 km south of St. Petersburg, Russian Fed.
Edited by undina-bird on 23-06-2011 05:56
Posted by Stephen R on 22-06-2011 23:40
I think it is Scaeva selenitica
Posted by undina-bird on 22-06-2011 23:48
Stephen R, thank you!
Posted by blowave on 23-06-2011 02:46
The spots look to reach the lateral margins, that would make it Scaeva dignota?
Posted by undina-bird on 23-06-2011 06:19
blowave, thank you for the opinion! I have no keys for Diptera, I don't see much difference between the two and now I really don't know... Is it important that on all photos of Scaeva dignota I found, dignotas have completely or almost completely light-yellow abdominal side of the body (while the one on my photo has large black spots on it)?http://denbourge.free.fr/Insectes_diptera_syrphidae_Scaeva_dignota.htm
(I understand that some may have mistakes, of course...)
Posted by blowave on 23-06-2011 13:33
Mark van Veen keys doesn't mention yellow at the edges of the abdomen for S. dignota.
S. selenitica spots do not reach the sides where for S dignota they normally do reach the margins.
Search for Scaeva dignota on this site, many other sites are not reliable.
You might post this in the syrphidae forum where it will get the attention of syrphidae experts.
Posted by undina-bird on 25-06-2011 01:15
Posted by Stephen R on 28-06-2011 13:41
It seems to me that the spots do not quite reach the edge of the tergites - there is a black line beyond them. According to Fauna Eur. S. dignota should not be found around St. Petersburg. Perhaps an expert will help :)
Posted by blowave on 28-06-2011 13:46
It's really quite difficult to tell if the spots do or don't reach the margin.
I wonder if undina-bird could post a closer crop of the pic viewing from the top? The angle from underneath might be giving a false impression.
I think if it could be seen for sure an expert might have replied by now.
Posted by undina-bird on 28-06-2011 21:46
> I wonder if undina-bird could post a closer crop of the pic viewing from the top? The angle from underneath might be giving a false impression.
This one the most "from the top" view I've got. Here is original size. Hope this helps.:)
There are black lines, though very thin ones?
Unfortunately, there is no S.dignota in the gallery on this site to compare, only S.selenitica http://www.diptera.info/photogallery.php?album_id=49&rowstart=780
Identified as Scaeva dignota — http://www.diptera.info/forum/viewthread.php?forum_id=7&thread_id=12115
Posted by blowave on 28-06-2011 22:01
The spots certainly look to reach the side margins to me!
Look at these..
undina-bird, you can make the links clickable by highlighting the link then click on the icon at the bottom of the post which is a circle with an arrow. :)
Posted by Menno Reemer on 29-06-2011 09:13
In certain specimens of S. selenitica the yellow maculae also reach the side margin, so the character is not reliable for distinguishing these species. It can only be used as a first indication: in S. dignota they always reach the side margin, in S. selenitica only in some specimens.
While males can be quite easily distinguished by the angle between the eyes on the frons, distinguishing thhe females is much harder. You need to take measurements of the width of the face relative to the width of the head, in frontal view.
I'm afraid this is not possible with these pictures. My gut feeling, for what it's worth, says this is S. selenitica...
Posted by undina-bird on 30-06-2011 19:28
Thank you very much to all! :)
Menno Reemer, that's right, I don't have frontal view. Thus, let it be Scaeva selenitica.