The genus Besseria Robineau-Desvoidy, 1830 with 15 described species (Tachinidae: Phasiinae) is distributed in the Palaearctic, Nearctic, and Afrotropical Regions. A new species, Besseria macrocerca sp. nov., is described from the western and southern regions of Iran. This species is diagnosed and illustrated based on both male and female specimens, with particular emphasis on distinctive morphological characters and male terminalia, notably the elongated cerci. An updated key to the Palaearctic Besseria species with a stalked r4+5 wing cell is provided, along with a key to three species of the genus known from Iran. Distributional data and revised records of previously known Iranian species are also presented. Previous records from the country include only two confirmed species, with some doubtful identifications. This study significantly improves knowledge of Besseria diversity in Iran, confirming the presence of three valid species in the country.
Gilasian et al. (Mon,) studied this question.