crepusculous

CIDE DICTIONARY

crepusculous, a. [Cf. F. crépusculaire.].

Pertaining to twilight; glimmering; hence, imperfectly clear or luminous. [1913 Webster]
"This semihistorical and crepuscular period." [1913 Webster]
Flying in the twilight or evening, or before sunrise; -- said certain birds and insects. [1913 Webster]
"Others feed only in the twilight, as bats and owls, and are called crepuscular." [1913 Webster]

For further exploring for "crepusculous" in Webster Dictionary Online