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Found two similar specimen of this St. Marks fly on 11.5.2025 in Pötzleinsdorf near Vienna.
I could not identify the species with this color so far. Is this just a variant?

Any informations appreciated!

Thank you very much,

Mike

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The only female Bibio with that red/black coloured scutum I've seen was B. clavipes. But this is a autumn species and it's more slender than yours.
It could be a Bibio reticulatus with an aberrant colouration as other characteristics match.

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Thank you eklans,

Yes, I have also spotted Bibio clavipes in the meanwhile. Looking at GBIF (https://www.gbif.org/species/1590805), most sightings (728) are reported in September, but there are also about 10 sightings in May (if ID is correct).
Is the body shape (slender) a distinctive feature?
If it is B. reticulatus, then I got two red specimen and no black one so far....

Thanks,

Mike

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Sounds interesting, Mike: can you point me to the May clavipes in GBIF? Theo's key in Vliegenmapper says that July could be the earliest date - mine are from October/November.
And all my female reticulatus have a black scutum - some were spotted while copulating, so ID should be correct.

And yes, slender is a characteristic of clavipes - I've translated this from BIBIONIDAE DE LA FAUNE BELGE by Jan Verbeke (Bruxelles):

"Small, slender, mainly yellowish species.
Hyaline wing, with a non-pigmented membrane, pale veins, and reduced stigma.
Thorax and legs yellow: tarsi I and II slightly darkened.
Abdomen brownish; body pilosity yellowish... Size: 6 mm."

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Thank you Eric!

Here you go: https://www.gbif....05/metrics
I fear that the sightings cover whole Europe, with south of France showing the most southern sighting.

The second specimen from may is also not very slender, slightly darker, but with same spots on the thorax...


Greetings,

Mike

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Hi Mike, I cannot comment the images at GBIF, but I can attach a small collage of a female Bibio clavipes of Oktober 2020. Regarding your fly: I think now that it's probably Bibio varipes. This one should have a bulge or callus like an inverted V between the eyes. Maybe you can see it in the original photo.