Three yellow sandshell mussels, Lampsilis teres (Rafinesque, 1820), were observed in Lake Tuscaloosa, Alabama, and the temporal display pattern of their mantle-flap lures was investigated in situ. All three gravid females fully displayed their mantle-flap lures after dark during each nighttime visit (N = 3) but none displayed their lures during daytime (N = 3). An encounter between a mantle-lure and a largemouth bass was observed. These observations are the first reported of in situ mantle-flap lure displays and fish host encounters for L. teres, and support previous studies of diel display patterns in other mantle-lure displaying mussels. This diel lure display may be related to the ecology of the fish hosts they seek to attract. Future daytime and, especially, nighttime field observations of bivalve mussels with mantle-flap lures may greatly improve understanding of their reproductive ecology.