A new species of Tequila Giant Skipper Aegiale C. Felder & R. Felder, 1860 (Lepidoptera, Hesperiidae, Megathymina) from Sonora, Mexico

<i>Aegiale</i> C. Felder & R. Felder, 1860 has traditionally been treated as a monotypic genus of Giant Skippers (Hesperiidae: Megathymina), represented by <i>A. hesperiaris</i> (Walker, 1856), which occurs from northern to central Mexico, mostly east of the Sierra Madre Occidental mountain range. Here, we describe a second species, <i>Aegiale occidentalis</i> KC, McGuire & Shirey, <b>sp. nov</b>., from Sonora, Mexico, occurring in the Sierra Madre Occidental. Morphological comparisons, including female genitalia, were used to diagnose the new species. <i>Aegiale occidentalis</i> <b>sp. nov</b>. differs from <i>A. hesperiaris</i> in dorsal forewing coloration, with fully orange apical and discal cell spots, and in female genitalia, including shorter papillae anales and a reduced sterigma. We provide illustrations of the habitus and female genitalia of both species, a key to differentiate them, and a key to distinguish <i>Aegiale</i> from other Megathymina genera. The discovery of <i>A. occidentalis</i> <b>sp. nov</b>. expands the known diversity of the genus and highlights underexplored montane regions in northwestern Mexico, with implications for the biogeography of agave-feeding Megathymina.