Opalinus: = opalescent; q.v.
Opaque: without lustre: not transparent.
Operaria: the workers in Hymenoptera.
Operative: in working order or actually working.
Opercula: two plates covering the vocal structure of Cicada, beneath.
Operculum: a lid or covering: in Diptera, the chitinous envelope covering the lower part of the muscid mouth; the labrum-epipharynx of Dimmock: the scutes covering the meso-thoracic stigmata: in Aleurodidae, the lid-like structure closing the vasiform orifice; q.v.
Ophthalmic: relating to the eye.
Ophthalmotheca: that part of the pupa that covers the eyes.
Opisthogoneate: having the organs of generation at hind end of body.
Opisthogonia: the anal angle of the secondaries.