A new species of Alavesia (Empidoidea: Atelestidae), Alavesia wimpala sp. nov. is described from the mid-Cretaceous amber of Myanmar. Together with the recently described Alavesia longistylata H. Zhang & Wang in Zhang et al. 2020 and A. longicornuta Sinclair & Grimaldi, 2020 the herein described species Alavesia wimpala sp. nov. forms a distinct group of Alavesia Waters & Arillo, 1999 which we consider deserving a subgeneric level. Subgenus Pennonalavesia subgen. nov. is introduced here comprising three species. Males of these species have a very prolonged third segment of stylus bearing a long-oval pennon. The palpus is prolonged and blade- or ribbon-shaped. A catalogue to all 19 species of the genus is given as well as a key to Alavesia (Pennonalavesia subgen. nov.). The function of the prolonged antenna in display and courtship is discussed. Most probably the triangular shape of the wings with its broad base allows a hovering flight in these species to present the pennons at the end of stylus. These characters indicate a high derived courtship behaviour in these flies in the Cretaceous period. On the other hand a possible raptorial behaviour of the new species is suggested.