Vespertilian

vespertilian \ˌves-pər-ˈti-lē-ən, -ˈtil-yən\ adjective: of, relating to, or resembling a bat

Etymology: Latin vespertilio bat, from vesper evening, evening star

Vespertilian creatures are vespertine. What would you call a matutinal creature? A matutin? Doesn’t have quite the same poetry.