BACKGROUND: Cytochrome oxidase subunit I (COX1) DNA sequences are widely used as a means of identifying Eukaryotic species, but in some taxonomic groups, such as the louse flies (Diptera: Hippoboscidae), there are many species that have not been sequenced. Until very recently (Wawman, 2025), Pseudolynchia garzettae (Rondani, 1897) had no sequences in either of the two main databases, NCBI GenBank and International Barcode of Life v3 (BOLD), but there are multiple sequences identified only to the level of the genus Pseudolynchia. METHODS: A Nightjar Louse Fly Pseudolynchia garzettae, was taken from an adult male European Nightjar Caprimulgus europaeus (Linnaeus, 1758), in Wales, United Kingdom, identified on the basis of its morphology and sequenced. The sequences were compared to all of the high-quality published COXI sequences for the genus Pseudolynchia. RESULTS: A 662 bp mitochondrial COX1 DNA sequence was obtained, confirming the sequenced fly as a separate species to all of the other sequenced specimens, which were all a single species Pseudolynchia canariensis (Macquart, 1839). A detailed morphological description of the fly and a differential diagnosis table is provided to aid researchers working with species in this genus. CONCLUSIONS: The DNA sequence supports the current taxonomy that places P. garzettae in the genus Pseudolynchia with P. canariensis, within the same clade as the genus Icosta. GRAPHICAL ABSTRACT: [Figure: see text]