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Seen today on Salix caprea flowers in forest area bordering with former agricultural enclave [returned to nature]. Thank you for help to ID

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Picture 2

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picture 3

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picture 4

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I am going to guess Gonia divisa (from the large orange abdominal markings, orange face and lack of grey dusted bands on the abdomen) but I would prefer Theo to confirm it because this is a tricky genus :)

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It looks like Gonia vacua for me.

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Ahh, there you are ... experience :)

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This is one of the few Gonia I did not see so far.

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Gonia vacua is not reported from the Netherlands. So this leaves me with a questionmark and want for confirmation.

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Other Central Europaen species have black longitudinal stripe broadening towards the back, with tergite 5 completely black, not like in these photos. Gonia capitata is an exception, but it is active not in spring, and looks a little different. Of couse, Theo commen needed.

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Sorry, i missed this one.

Gonia vacua is not dutch and not to be expected. I'm aware it is not uncommon in, say, Lithuania.

This really is divisa, but I totally agree it was very difficult to call.
Light divisa can be very similar to vacua.
However, in the second pic you can see that the anus is all around black, which I've never seen in vacua. I totally agree it is impossible to see unless you very specifically look for it (and even then..). Moreover, the head is yellow in all pictures. Colouration of head can be misleading in pictures, but here it is constantly yellow, implying divisa rather than vacua. Finally, the dusting on tergites in nearly completely lacking. In vacua, it is sparse in a narrow band, but it is there.

So for me no reason to find a new species for NL, alas.


Theo

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The virtual lack of whitish dusting is very nicely shown in the second picture.


Theo

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Another possible useful feature might be that the humerus is totally yellow in divisa (I only checked males, this is a male), whereas in vacua it darkened on anterior half, and thus would show much less light in a picture.

In the hand, the difference between the two is obvious and straightforward based on the hairs on the parafacialia.
If it would be possible to get a blowup of the third pic, we might check that as well.


Theo

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Thank you very much Theo for the extensive explanation. I will add a detail of pics 3 as requested.

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Gonia divisa is common in my area in spring and I have large collection of this species. But I have never seen such an aberrant specimen, therefore I treated absence of intensive dusting as trick of the light. Very nice experiance, thank you very much.

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This blowup confirms divisa.

Erikas is quite right that this one was quite exceptional.
By the way, in my experience divisa is much darker in Finland than in NL. Lithuania might be intermediate

Theo

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So Jan, could you please provide more data on locality and date ?
G. divisa is pretty rare in NL. I'd like to add the record to the database


Theo

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The details are:
Date: 9 april 2011
Time: 17:08 hrs
Locality: Veluwe-Planken Wambuis, The Netherlands
Habitat: Edge of old Beech forest (Fagus sylvatica] with several Salix caprea all in full bloom bordering seminatural grassland -heath area with many Solidago plants. [area is a former agricultural enclave returned to nature more than 15 years ago]
Weather: sunny clear sky 17 degree Celcius.
Seen on flowers of Salix caprea at about 1,5 m.

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Thank you,


Theo