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Damselfly ID - Helsinki (Finland) (1 Viewer)

Dave Pearson

Dave Pearson

Well-known member
I am still agonising over the ID of a damselfly I photographed near Helsinki in late June, 2016. I believe it is either Arctic (Coenagrion johanssoni) or Variable (C. pulchellum). Would anyone like to confirm?
 

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Can we eliminate hastulatem ?

Don't think it's Variable, it has solid antehumeral stripes and if it were johanssoni I'd expect no stem on S1-2, yours has a thick stem.


A
 
I don't think it's Variable Damselfly either - the pronotum is not strongly tri-lobed. I've no field experience of either hastulatum or johanssoni so don't know how the segment patterns vary from the drawings in my books.
 
The mark on S2 looks U shaped & not spearhead shaped which would point towards C. johanssoni but I don't think we can conclude a positive id without further photos!


Shane
 
I'm not saying it is C. johanssoni for sure as you point out there are features that support C. hastulatum but I think further photos are needed, particularly (& unusually) a side-on one to help id!


Shane
 
Sorry, that is the only photo I have.

I believe there can be some variation in the mark on S2, particularly with C. hasulatum but I cannot find any other images that show it to this extent.
 
The 2 photos showing S2 are not slightly different but significantly different so I don't see how a definitive id can be made without a side view ....... & if there is a black cat or sphinx in the mark then it's C. johanssoni, if not C. hastulatum? Unfortunately, we don't have a side view to confirm!


Shane
 
I'm pretty certain this is Coenagrion hastulatum, showing just a little more black than typical. Thus the marking on abdominal segment S3 is spear-shaped (more blunt-ended in johanssoni), and the pronotum is also quite pointed (more smoothly rounded in johanssoni). The shape of the pronotum is a useful feature for IDing the blue damselflies.
 
Adrian_P said:
I'm pretty certain this is Coenagrion hastulatum, showing just a little more black than typical. Thus the marking on abdominal segment S3 is spear-shaped (more blunt-ended in johanssoni), and the pronotum is also quite pointed (more smoothly rounded in johanssoni). The shape of the pronotum is a useful feature for IDing the blue damselflies.
Click to expand...

Called the 'prothorax' by Americans I believe?



A
 
aeshna5 said:
Not quite the same! The prothorax is the first of the 3 thoracic segments whereas the pronotum is the dorsal part of the prothorax.
Click to expand...

'Schooled' as the American's like to say, thanks aeshna.

Would the culmen of a birds bill be a valid comparison?


A
 
andyadcock said:
'Schooled' as the American's like to say, thanks aeshna.

Would the culmen of a birds bill be a valid comparison?


A
Click to expand...

I can see where you're coming from with this analogy, though of course the exoskeleton of an insect isn't really comparable with a bird's bill.
 
I am sure hastulatum is most likely. You can just see the horizontal stripe on the side of S2, but none of the hastulatums I have seen in Scotland or Sweden looked quite like this. Just goes to show what a night out in Helsinki can do to you.

Lee
 
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