n. plDiurna(Zoöl) A division of Lepidoptera, including the butterflies; -- so called because they fly only in the daytime.
Century Dictionary and Cyclopedia
diurnaIn entom.: The butterflies; the diurnal Lepidoptera or Rhopalocera, as distinguished from the Crepuscularia and Nocturna, or Heterocera (moths). They correspond to the old Linnean genus Papilio, and are so called because they show themselves only during the day.
diurnaAn occasional name of insects which in the mature state live only a day or so, as the Ephemeræ or day-flies.
Webster's Revised Unabridged Dictionary
NL., fr. L. diurnus, belonging to the day
Acta diurna and Acta senatus, used by Tac.
"The Student's Companion to Latin Authors" by George Middleton
The Acta Diurna were published by authority, and formed an official gazette.