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. Osmaterium -ia: fleshy, tubular, eversible processes producing a penetrating odor, capable of being projected through a slit in the prothoracic segment of certain Papilionid caterpillars, and from openings elsewhere in the bodies of other forms. {Scanner's comment: currently the only spelling I can find is "osmeterium". This given spelling is almost certainly an error on someone's part. Not only do the earliest books that I can find spell it "osmeterium", but the Greek root is "osme".} Osmosis: the tendency of liquids to pass or diffuse through a membrane or septum. Osselet: = ossicle; q.v. Ossicle: a small nodule of chitin resembling a bone. Ossicula: small corneous pieces that serve in the articulation of the wings to the thorax. Ostia: the slit-like openings of the heart. Ostiolar canal: a marginal furrow leading from the ostiole. Ostiole: in Heteroptera, the openings at the sides of meso- and metathorax, through which an odoriferous fluid is excreted. Ostium: singular of Ostia; q.v. -osus; an affix, signifying saturation, or the possession of the quality expressed in the stem word. Otocyst: an auditory or ear-like vesicle. Otolith: a little ear-bone: granules or concretions found in an otocyst. Outer lobe: of maxilla = galea; q.v. Outer margin: the outer edge of wing, between apex and hind angle. Ovo, Ovum: the eggs; an egg. Ova glebata: eggs laid or concealed in lumps of dung. Ova imposita: eggs laid in the substance that is to serve as food for the larva. Oval: egg-shaped, with both ends similar. Ova pilosa: eggs that are covered with hair: usually from the abdomen of the female. Ovarian tube: a tubular structure in which are developed the cells forming the future ova: a single one of the mass which, taken together, form the ovaries. Ovaries: a mass of ovarian tubes, lying one on each side of the body cavity of the female, in each of which tubes eggs or ova are developed: the individual tubes of an ovary all converge to one oviduct. Ovariole: an ovarian tube: q.v. Ovary: singular of ovaries; q.v. Ovate: in outline, egg-shaped or oval.