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#1 2016-12-29 20:57:12

anymarks
DF Members
Name: Neil Marks
From: Norfolk
Registered: 2009-08-07
Posts: 93

Thereva plebeja ?

This seems to key to Thereva plebeja.
However - as usual - I have never seen a real life aedeagus on a therevid specimen that vaguely resembles the nice, simple drawings in the keys.

I have just soaked another specimen to remove the concretions and the whole lot turned to a formless mass. So, before trying again I would be appreciative of a second opinion on this one.

Regards, Neil


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#2 2016-12-29 22:01:52

conopid
DF Members
Name: Nigel Jones
From: Shrewsbury
Registered: 2008-02-27
Posts: 619
Website

Re: Thereva plebeja ?

I can see what you mean about the diagrams. On balance I'd say it matches the diagram and description of the aedeagus in Stubbs and Drake better than for the other species. However I've never seen this species so cannot be more positive.


Nigel Jones
Shropshire

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#3 2016-12-30 12:20:34

pbrighto
DF Members
Name: Phil Brighton
From: Warrington
Registered: 2011-10-21
Posts: 339

Re: Thereva plebeja ?

The black on tergites 2 and 3 seems limited in extent so at couplet 5 it would go to 6 rather than 8.   That would seem to lead to the commoner T. nobilitata. The aedeagus shape does not seem all that different from the S&D diagrams.  Martin Harvey's checklist on the Soldierflies and Allies Recording Scheme website gives the ID difficulty grade as 4 for plebeja, requiring examination of a voucher by a expert, and it would be worth contacting him to see if there's anyone suitable in your area.   It would also be worthwhile considering the habitat that the specimen was caught in.

Last edited by pbrighto (2016-12-30 12:34:12)

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#4 2016-12-30 19:36:07

anymarks
DF Members
Name: Neil Marks
From: Norfolk
Registered: 2009-08-07
Posts: 93

Re: Thereva plebeja ?

Thanks Nigel & Phil

I was drawn to T.plebeja by the two rows of anteroventral bristles on the hind femur and the presence of posteroventrals (all my specimens of T.nobilitata have the usual 3 rows and no posteroventrals).
The hairs down the mid line of the tergites are all black, and those on the sternites are all pale.

I was really just perplexed by the aedeagus - I didn't want to go wrecking this one if it could be avoided smile

(All of my T.nobilitata have been taken in late June - this one was 21st August but from the same habitat i.e a line of trees on the edge of grazing marshes near the Norfolk coast)

Regards, Neil

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#5 2016-12-30 20:42:13

conopid
DF Members
Name: Nigel Jones
From: Shrewsbury
Registered: 2008-02-27
Posts: 619
Website

Re: Thereva plebeja ?

I don't think you need to dissect this specimen. There is easily enough of the aedeagus visible to enable an accurate ID. I'll see if I can post an image of a nobilitata aedeagus later to see if that might help.


Nigel Jones
Shropshire

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#6 2016-12-30 21:05:07

conopid
DF Members
Name: Nigel Jones
From: Shrewsbury
Registered: 2008-02-27
Posts: 619
Website

Re: Thereva plebeja ?

Here is the aedeagus of Thereva nobilitata. I'd say that your specimen is different - it lacks the broad curved section at the base. But Phil is right, get the specimen checked over by an expert, or at least someone who has specimens of both species.

There is another image here by Janet Graham: https://www.flickr.com/photos/130093583 … 2/sizes/o/

PS - I have added an image showing nobilitata v your specimen - they are clearly different.


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Last edited by conopid (2016-12-30 21:09:16)


Nigel Jones
Shropshire

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