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Moscow region, 10 june, 10-11mm.

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Nikita - I think (from memory) that it is impossible to distinguish S ribesii and S vitripennis females. Definitely Syrphus sp, but I'd have to go to my books to get any further.

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Thank you Susan.
In my key S. vitripennis female - f3 - black 2/3 from base,
S. ribesii female - f3 - all yellow. I can't understand whether black ring on f3 on photo is result of wing shadow of flash light or it is realy black.
Could you?

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Susan, I need medical treatment to stop gaps in my memory, - fly is collected!
f3 - clearly black in base 2/3.
So, according my key (the old one as you remember) it is Syrphus vitripennis.
Thank you again.

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Nikita

The black on the hind femora was the character I was thinking of, but knew you could only distinguish one of the sexes this way and the other is indistinguishable. Must be males you can't distinguish. I'll try to check my key when I have time (or someone like Gerard will enlighten us).

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This is a female S. torvus: the hairs on the eyes are short (as usual in females), but clearly visible. In this species the female - as in S. vitripennis - also has partly black hind femora.

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Thank you Menno.

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It's torvus ok but the term short (in short hairs) raises a question. How short is short and under which microscope or magnification? A fundamental problem of working with words not pictures And how about setulae -sort setae? Calling a sore back lumbago does not solve the problem.

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In this case it doesn't really matter, because S. torvus is the only one of these three species with hairy eyes. The narrowness and pale fasciae on the abdomen also suggest it's torvus. How narrow is narrow? How pale is pale? This is a matter of experience.
In preserved specimens you could also check the microtrichia on the wing: entirely covered in S. torvus & S. ribesii, while large parts are bare in S. vitripennis.

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Hi,

Thanks for all this, because one would have a hard work to express it so clearly within a key.