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The Society for the study of flies (Diptera)

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#1 2019-09-03 11:20:16

toshgallego
Registered user
Name: tony fergus
From: Musselburgh, scotland
Registered: 2019-08-09
Posts: 27

chorisops nagatorii or tibalis?

14/08/19 Musselburgh small wooded area near Ravenshaugh. If it is the former then is it not out of place in Scotland?


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#2 2019-09-03 17:01:53

Tony Irwin
DF Members
Name: Tony Irwin
From: Norwich
Registered: 2008-03-01
Posts: 834

Re: chorisops nagatorii or tibalis?

Pictures 1 and 3 show a Beris morrisii female (six dark spines on scutellum, pale legs, narrow frons). Picture 2 shows Chorisops tibialis female (4 pale spines on scutellum, frons black, "corners" of thorax dull yellow)

Last edited by Tony Irwin (2019-09-03 17:02:57)

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#3 2019-09-03 18:24:52

toshgallego
Registered user
Name: tony fergus
From: Musselburgh, scotland
Registered: 2019-08-09
Posts: 27

Re: chorisops nagatorii or tibalis?

damn...looking at the pic metadata they were shot within 1 minute. I thought I was dealing with the same creature! Thanks for clearing that up Tony.

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#4 2019-09-03 18:27:02

toshgallego
Registered user
Name: tony fergus
From: Musselburgh, scotland
Registered: 2019-08-09
Posts: 27

Re: chorisops nagatorii or tibalis?

BTW I can see the differences now!

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#5 2019-09-05 16:45:40

AliCullaloe
DF Members
Name: Ali Shuttleworth
From: Fife, VC85
Registered: 2014-08-20
Posts: 94
Website

Re: chorisops nagatorii or tibalis?

Hi all

For what it's worth I've recorded female nagatomii from Dalgety Bay, Fife (19/8/2017) in a small wooded coastal area, so the location is not problematic.

Stephen Falk's flickr page has good photos of both species

My tuppenceworth:
(1) the late date of mine in late August was more consistent with nagatomii than tibialis, which has an earlier flight period. This is even later.
(2) clear yellow humeri in the key couplet leads to nagatomii and those seem to me very pale. The tibialis I've seen are all no more than a bit yellow-ish at best
(3) I'm not convinced you can determine the frons colour from the oblique view on this photo. I could barely discern the nagatomii frons as green even moving it around under a microscope
(4) The abdomen does look a bit dark, but if I flip back and forth between the photo and flickr I can't say I see a clear difference. I struggled with the abdomen pattern even with the nagatomii on a pin and comparing to museum specimens of tibialis. I'll dig out a pic of mine in a minute

I'm sure Tony is much more experienced than me but since I've had reason to spend a lot of time on the pair I thought I'd share what I found.

Cheers
Ali

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#6 2019-09-05 16:52:57

AliCullaloe
DF Members
Name: Ali Shuttleworth
From: Fife, VC85
Registered: 2014-08-20
Posts: 94
Website

Re: chorisops nagatorii or tibalis?

I posted my nagatomii to the DF gallery here:
http://www.dipteristsforum.org.uk/img/g … 691493.jpg

(I only realised afterwards that you're both Tony! I'm sure you got it though)

Cheers
Ali

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#7 2019-09-05 18:04:12

Tony Irwin
DF Members
Name: Tony Irwin
From: Norwich
Registered: 2008-03-01
Posts: 834

Re: chorisops nagatorii or tibalis?

I may be more experienced, Ali, but that doesn't stop me from being wrong! wink Regarding the dates, tibialis does occur through to late September. I agree that the humeri do look a bit too pale for tibialis, but the general colouration of the thorax is not as bright as the nagatomii here. The abdominal pattern is a bit ambiguous and the frons colour does depend on lighting, I agree. On reflection, I'd call this Chorisops species to be safe, but it would be good to have some input from others!

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#8 2019-09-05 18:59:22

AliCullaloe
DF Members
Name: Ali Shuttleworth
From: Fife, VC85
Registered: 2014-08-20
Posts: 94
Website

Re: chorisops nagatorii or tibalis?

Thanks, Tony.

I'm very glad I had a voucher specimen!

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