Ooblast: the primitive germinal nucleus of an egg.

Oogenesis: the process of egg-formation.

Oolemma: the cell wall of an egg: see vitelline membrane.

Ootheca: the covering or case over an egg ma.s.s, as in certain Orthoptera: see egg case.

Opacus: opaque; a surface without any l.u.s.tre.

Opalescent: with a bluish white l.u.s.tre, as in opals.

Opalinus: = opalescent; q.v.

Opaque: without l.u.s.tre: 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 a.n.a.l angle of the secondaries.

Opposite: placed over against, or opposed to.

Optic: relating to the organs of vision.

Optic ganglia: are at the sides of the procerebrum and innervate the compound eyes.

Optic lobes: the laterals lobes of the procerebrum in which are centered the nerves supplying the organs of vision.

Opticon: the first of a series of three ganglionic swellings in the optic nerve: see epiopticon and periopticon.

Optic segment: =procerebral segment; q.

Optic tract: is the perceptive portion of the compound eye.

Ora: a border: specifically in some Coleoptera, the lateral margin of prothorax.

Ora coleopterorum: the margin of the elytra.

Orad: toward the mouth.

Oral: pertaining to the mouth.

Oral cavity: the mouth; = buccal cavity.

Oral fossa: in Mallophaga, a furrow lying in front of the mandibles.

Oral segment: that ring or segment which bears the mouth.

Orbicular: round and flat, the diameters of the plane equal: in sonic moths, a round or oval macula in the median cell.

Orbit: an imaginary border around the eye: in Diptera the orbits are divided into vertical or superior; frontal and facial or anterior; of the cheek or inferior; occipital or posterior.

Orbital sclerite: a narrow sclerite encircling some eyes.

Order: one of the primary divisions of the Cla.s.s Insecta, based largely on wing structure and then usually ending in -ptera.

Ordure: excrement; usually applied to such as is foul or offensive.

Orichalceous: = aurichalceous; q.v.

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 a.n.a.l 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 pa.s.s or diffuse through a membrane or septum.

Osselet: = ossicle; q.v.