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Location: Midwest Sweden (Dalsland)
Date: 2008-JUN-18
Size: ~5-6 mm (estimated)

This fly walked back and forth of a fallen trunk (alnus or maybe aspen) and displaying its wings, sometimes both at the same time and sometimes only just the right or the left wing. It wasn't waving the wings like Sepsis, but unfolding them like a pocket knife unfolds a blade. A few times when it got disturbed it slided away side-ways from me instead of just flying off. It was moving most of the time making it hard to focus the camera.

I thought all these four photos where of the same fly, but now I start wondering about the last one (pic #4). Notice the white? spikes in the back of the head on pic #3.

It resembles Prochyliza a bit, but I ain't sure about the family.

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Pic #2

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Pic #3

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Pic #4

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This might be Homalocephala (Ulidiidae): the white bristles and the absence of a marking in photo 4 may just be lighting effects. If so, a good find as these are rare.

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Thanks Phil! In case you are right there are 7 species recorded from Sweden:
- Homalocephala albitarsis
- Homalocephala angustata
- Homalocephala apicalis
- Homalocephala bimaculata
- Homalocephala biseta
- Homalocephala biumbrata
- Homalocephala mamaevi

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wait for Valery. :)

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I am and I have several threads that need an answer, but I realize even the heavy dudes must have vacation, specially this time of year B)

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Any Ulidiidae experts on board now? B)

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Almost certainly Homalocephala biumbrata Wahlberg. @Almost@ is because halteres are not visible; Elena Kameneva det.

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Thank you very much and send my regards to Elena. I attach an additional terrible photo, but maybe enough to show the whitish haltere. I think the light haltere also shows through the wing on the other photos as well. I hope this confirms the determination

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yesss!

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Thanks again! :D