Description of a new species of Speiser , 1905 (Diptera: Hippoboscidae) from Southern Vietnam with the updated key to the subgenus .

The family Hippoboscidae, commonly known as "louse flies," comprises pupiparous Diptera that are ectoparasites of birds and mammals, with significant impacts on their hosts and epidemiological importance. The louse fly fauna of Vietnam is relatively understudied compared to other countries in the Southeast Asia region. In this study, we describe a new species of the genus Speiser, 1905 (Diptera: Hippoboscidae), , collected from the lesser coucal (Gmelin, JF, 1788) in Cat Tien National Park, Vietnam. This new species is distinguished from other species by the morphology of laterite 3, wing length, arrangement of wing microtrichia, body coloration, and its geographical distribution. Additionally, we provide an updated key to the subgenus Speiser, 1905.