ike ridges on caterpillars.

Onisciform: shaped like a wood-louse, Oniscus sp.; applied to certain
Lycaenid and other caterpillars.

Ontogenetic: relating to the development of the individual.

Ontogeny: the development of the individual as distinguished from
that of the species: see phylogeny.

Onyches: claws of tarsi.

Onychium -ia: small processes between the tarsal claws in many
Diptera; see empodium: a more or less retractile process on the feet of
some beetles: in Hymenoptera, the apical tarsal joint bearing the
claws: see also arolium and pulvillus.

Ooeblast: the primitive germinal nucleus of an egg.

Ooegenesis: the process of egg-formation.

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

Ooetheca: the covering or case over an egg mass, as in certain
Orthoptera: see egg case.

Opacus: opaque; a surface without any lustre.

Opalescent: with a bluish white lustre, as in opals.

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.

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 ma