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#1 2012-07-14 00:42:23

quercuscorticis
DF Members
Name: Carl Farmer
From: Taynuilt, Argyll
Registered: 2008-10-04
Posts: 8
Website

Syrphus eye hairs

So many male Syrphus that I find key out to S torvus, due to the hairy eyes, that I began to get a bit suspicious and checked a wing for microtrichia today.  Sure enough, the second basal cell was mostly bare of microtrichia, ruling out S torvus.

The other Syrphus species are said to be bare-eyed in Stubbs & Falk and in all other sources that I can locate, except for an obscure comment on http://www.wildaboutbritain.co.uk/forum … orvus.html where it is said "The only problem is S.ribesii and S.vitripennis also have scattered hairs on the eyes although less than S.torvus."

Is this correct, or are they totally bare-eyed?  I must say the specimen I'm currently looking at does not have the hairs quite as dense as usual, but they are close enough to fit the description "eyes densely hairy" rather than "eyes bare".

If the other species do have hairy eyes, it will still be easy to separate male vitripennis/rectus from torvus (only to have to discard the record due to not knowing whether it's vitripennis or rectus), but is there any way to separate male ribesii from torvus?

Many thanks

Carl

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#2 2012-07-14 15:26:13

Howard Bentley
Committee
Name: Howard Bentley
Registered: 2008-07-07
Posts: 774

Re: Syrphus eye hairs

The key to Syrphus in van Veen (Hoverflies of Northwest Europe) begins by separating those with a quarter or more of the second basal cell lacking microtrichia from those with the second basal cell entirely covered. The former group includes S. vitripennis while the latter includes S. torvus and S. ribesii. Characters given for torvus are then "eyes with numerous hairs, in male long and dense, in female shorter; femur 3 black on basal three-quarters. 10-13 mm", while the alternative says "eye with at most some very short scattered hairs". This seems to me to lead quickly and unambiguously to correct identification of S. torvus specimens.

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#3 2012-07-14 19:07:29

quercuscorticis
DF Members
Name: Carl Farmer
From: Taynuilt, Argyll
Registered: 2008-10-04
Posts: 8
Website

Re: Syrphus eye hairs

Thanks Howard.  I've ordered the book.
Carl

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