Crepuscular refers to animals or insects that are active during the twilight hours, just before sunset or just after sunrise ^{1 2}. For example:

• "At sunset, the entomologists study the crepuscular insects as they move across the beach."
• "Deer are crepuscular, meaning that they are most active at dawn and at dusk."
• "The crepuscular hour is my favorite, when the sky turns deep red and purple and the noise of the day quiets to a whisper."