Photuris lucicrescens Crepuscular   animals  are those that are active primarily during  twilight , that is during  dawn  and  dusk . [ 1 ]  The  word  is derived from the  Latin  word  crepusculum , meaning "twilight." [ 1 ]  Crepuscular is, thus, in contrast with  diurnal  and  nocturnal  behavior. Crepuscular animals