Occiput: that part of the head behind the vertex: in Diptera, the whole posterior surface of the head: in bees, the s.p.a.ce between the vertex and the neck.

Occlusor: applied to muscles which close an opening; e.g. spiracles.

Occult -us: hidden; concealed from superficial view.

Ocellar bristles: in Diptera, are situated close to the ocelli, usually directed forward: often absent.

Ocellar ribband: a crescent-shaped, smooth thin belt across the eye region in b.u.t.terfly chrysalids.

Ocellar triangle: a triangle, indicated by grooves or depressions, on which the ocelli are situated; Diptera.

Ocellate: eye-like in appearance: in Lepidoptera, spots on the wings, bordered by a colored iris or ring, and usually with a pupil.

Ocelli: plural of ocellus; q.v.; = stemmata.

Ocelligerous: supplied with, or bearing ocelli.

Ocellus: a simple eye, consisting of a single convex or bead-like lens, which conveys an image to a retina.

Ocelli occur in larvae and, singly or in small groups, in adults: the compound eyes are made up of numerous ocelli.

Ochraceous: yellow with a slight tinge of brown [pale cadmium yellow and brown ochre].

Ochraeus -eus: = ochraceous.

Ochro-leucus: dilute ochraceous.

Ocular emargination: in Mallophaga, a lateral emargination of the head in which the eye is received posteriorly.

Ocular fleck: in Mallophaga, a small, intensely black spot of pigment in the eyes.

Ocular fringe: in Mallophaga, closely set small hair on posterior half of ocular emargination, sometimes extending on temporal margin.

Ocular lobes: of brain = procerebrum; q.v.

Ocular sclerite: the first or protocerebral segment of the head.

Ocular tubercles: in Aphids, are a group of prominent facets on the hinder part of each eye.

Oculi -us: the eyes: an eye: refers to the compound eyes.

Oculocephalic: applied to that pair of imaginal buds destined to produce the cephalic region in Hymenoptera.

Odona: toothed: applied to Odonata by Fabricius because of the long teeth on the maxilla and labium.

Odonata: net-veined insects with mandibulate mouth; head free; thorax agglutinate; wings similar, elongate, flat; metamorphosis incomplete; copulatory organs of male near base of abdomen, separate from the testes. {Scanner's comment: Dragon flies and damselflies}

Odonate: bearing toothed mouth parts, like those of dragon flies.

Odoriferous: diffusing an odor; applied to glands or secreting organs.

OEcology: see ecology.

OEdagus: the p.e.n.i.s.

OEnocytes: large yellow cells arranged segmentally in cl.u.s.ters, in each side of body cavity: a.s.sociated with blood and fat bodies.

OEsophageal bone: a plate below anterior part of oesophagus in Psocidae.

OEsophageal bulb: = sub-clypeal pump; q.v.

OEsophageal diverticula: = food reservoirs (q.v.); but more generally applied also to any sac-like structure connected with the gullet.

OEsophageal lobes: form posterior portion of brain or tritocerebrum.

Oesophageal valve: a funnel-like folding of the oesophagus, extending into the chylific ventricle in some insects, and forming a valve that controls the entrance of food into that organ: = cardiac valvule.

Oesophagus: the gullet: that part of the alimentary ca.n.a.l between the mouth and the crop.

Olfactory: pertaining to the sense of smell: those lobes of the deutocerebrum from which the nerves supplying the antennae arise.

Oligonephria: applied to insects with few urinary (Malpighian) tubes.

Oligoneura: having few wing veins: specifically applied in Diptera to Cecidomyids.

Olivaceous: with a tinge of olive-green, usually as a shading [olive green].

Omaloptera: the pupiparous flies.

Omia: the shoulders: the lateral anterior angles of an agglutinated thorax, when they are distinct:= see umbone: in Coleoptera; a corneous sclerite to which the muscles of the anterior c.o.xa are attached; also the lateral margin of the prothorax; also the lateral margin of the scutellum in Carabids and Dytiscids.

Ommateum: the compound eye.

Ommatidium -ia: one of the elements of which the compound eye is composed.

Omnivorous: a general feeder upon animal or vegetable food, or both.

Oncus -i: a welt: applied to welt-like 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.