A parasitic fly of the familly Nycteribiidae collected on a Plecotus auritus bat in Switzerland (Le chenit, Baume de la petite Chaux, Coll. P. Nyssen).
Female of the genus Nycteribia or Basilia (probably Basilia nana (thanks to Fardo Witsenburg and Daan Dekeukeleire for the additionnal ID information)
Scale : bodylength < 2mm