In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine/vespertinal, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daylight and of darkness, respectively. Some crepuscular animals may also be active by moonlight or during an overcast day. Matutinal animals are active only before sunrise, and vespertine only after sunset.
A red fox at dusk
A domestic cat at low light
Fireflies at twilight, long exposure
Ocelots are active at night, especially during dawn and dusk.
Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs.
Midtown Manhattan during civil twilight, demonstrating blue hour
Civil twilight in a small town in the Mojave Desert
Evening nautical twilight on Lake Ontario, Canada
Long exposure of nautical twilight in a small town in the Mojave Desert