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Thank you for you answer, specially for the first link. Although we don't see well the legs, this key conducts to V. Arenicola.
Indeed, V. gracilis is not similar. There's flattened scales on the abdomen. The wings are clear. The lateral tomentum on the upper abdomen is yellow, not orange. The thorax has a triangle of light tomentum in front of scutellum. The abdominal light bands of tomentum are white in the anterior part and yellowish at the abdominal end and above the scutellum.
It's not so important if "arenicola" must be considered as a species or just variety.

It helped a lot, thanks !