Oriental: in geographical zoology as used by Wallace, that part of the earth's surface including Asia east of the Indus River, south of the Himalayas and the Yangtse-kiang watershed, Ceylon, Sumatra, Java and the Philippines.
Orificium: the anal or genital opening.
Original type: is the actual specimen from which a published description is prepared.
Orismologia -y: the defining of scientific or technical terms.
Orthoptera: straight winged: an ordinal term applied to insects in which the primaries are not used in flight, but cover the longitudinally folded secondaries; mouth mandibulate; head set into prothorax, the latter free; metamorphosis incomplete.
Orthorrhapha: that section of Diptera in which the pupa escapes from larval skin through a T-shaped opening on back: see cyclorrhapha.
Orthorrhaphous: straight-seamed.
Os: the mouth of insects, in general.
Oscillation: a vibrating or swinging from side to side.
Osculant: intermediate in character between two groups or series.