O

Ob-. - A Latin prefix signifying in the way of, toward, and also reversal.

Obconical. - Of a reversed cone-shape-thickest part in front. (L. ob, and M.F. cone, - L. conus, a cone.)

Obcordate. - Inversely heart-shaped. (L. ob, and cor, the heart.)

Obese. - Unnaturally enlarged and distended, as if from disease or too much food; fat; fleshy; (L. obesus, ob, esum, to eat.)

Oblate. - Flattened this term is applied to a spheroid of which the diameter is shortened at two opposite ends. (L. ob, and latus, broad.)

Oblique. - Running sideways; when the longitudinal line is cut through at acute angles; slanting; neither perpendicular nor parallel. (L. obliquus, slanting.)

Oblique tergals. - Short muscles connecting the edges of the tergites of the abdomen. (L. obliquus, and tergum, the hinder part.)

Oblique sternals. - Very short muscles connecting the adjacent edge of the sternites of the abdomen. (L. obliquus, and from sternum, the breast-bone.)

Obliterate. - When the borders of spots, puncta, granules, etc., fade into the general ground colour, and when elevations and depressions, etc., are so little raised or sunk from the surface as to be almost erased. (L. ob, and litera, a letter.)

Oblongum. - Oblong. (L.)

Oblong. - having the longitudinal diameter more than twice the length of the transverse diameter; longer than broad. (L. oblongus.)

Obovate, Obovatus. - Reversed egg-shaped; inversely ovate. (L. ob, and ovum, an egg.)

Obscure. - Dark; abstruse; remote from observation; indistinct. (L. obscurus, from Skt. sku, to cover.)

Obscure-aeneus. - Of an indistinct bronze colour. (L. obscurus and aeneus, brazen.)

Obsolete. - When a spot, tubercle, etc., is scarcely apparent. N.B. - This term is often employed where one sex, kindred species, or genera, want, or nearly so, a character which is conspicuous in the other sex, or in the species or genus to which they are most closely allied. (L. ob, and soleo, to be wont to.)

Obsolete. - Almost or entirely effaced; not fully developed; indistinct. (L. obsoletus, obsolete.)

Obtect pupæ. - Pupæ which have the limbs and wings immovably fixed by a general hardening and fusing of the outer skin, or theca. (L. ob, and tectum, to cover.)

Obtected. - Covered. (L. ob, and tectum.)

Obtusa. - (Lacinia.) Rounded and not produced into a prominent or active point. (L. obtusus, blunt, obtuse.)

Obtuse. - Having a rounded termination; blunt; not pointed or acute. (L. obtusus, blunt.)

Obverse. - When an object is viewed with its head towards you. (L. ob, and verto, versum, to turn.)

Occipital foramen. - A large shield-shaped opening behind the head through which the œsophagus, nerve cords, and air tubes pass back to the body. (L. ob, and caput; and foramen, from L. foro, to bore.)

Occiput. - The back of the head, around the commencement of the collum. (L. ob, and caput, the head.)

Ocelli. - Simple eyes, small extra eyes, usually situated on the top of the head. The cuticle covering the eye is thickened like a lens. Below the lens there is a layer of transparent cells, continuous with the adjacent epidermal cells. (L. ocellus, a little eye.)

Ocellate, Ocellated, Ocelloid. - Furnished with round spots surrounded by a ring of lighter colour; resembling ocelli in appearance. (L., ocellus.)

Ocellus. - An eye-like spot of colour, consisting of annuli of different colours, enclosing a central spot or pupil. (L. an eye.)

Ochraceus. - Brownish-yellow in colour. (Gr. ochra, from ochros, yellowish.)

Octoon. - The eighth segment in insects. (L. octo, eight.)

Oculi. - Compound eyes. They consist of a large number (as many as several thousand) of simple eyes, closely packed together in the form of hexagons. The compound eye is, however, peculiar, in that the ommatidia are very narrow and elongate, and each one consists of only a few retinal (6-8) and vitreous cells. (Boas.) (L. oculus, an eye; L. oculeus, full of eyes.)

Oculi approximati. - Eyes closely set together. (L. oculus, and a, and proximus, near.)

Oculi distantes. - Eyes when separated by the brow. (L. oculus, and dis, separation, and sto, to stand.)

Oculi nudi. - Naked eyes, eyes without hair, marks, or covering. (L. oculus, and nudus, naked.)

Oculi pilosi. - Eyes which have the margins of separation thickly set with hair. (L. oculus, and pilus, hair.)

Oculi simplices. - Ocelli, simple eyes. - (L. oculus, and simplex, simple.)

Odoratus. - (Scent.) An undefined sweet smell. (L., sweet smelling.)

Œnocytes. - Large, yellowish cells, situated on each side of the abdomen (rarely found in the thorax) and held in place by the trachea. They are associated with the blood and fat. (Wielowiejski.) (Gr. oinos, wine, and kustis, a cyst.)

Œnocytes. - Glandular cells arising in segmental clusters from the ectoderm of the embryo just behind the tracheal invaginations. In the adult they are very small, and scattered about among the fat cells. Their function is not exactly known. (Gr. oinos, and kustis.)

Œruginous. - Bright green. (L. ærugo, rust of copper, verdigris.) See Æruginous.

Œsophageal valve. - An invagination of the fore-stomach which projects into the cavity of the mid-intestine. (Schneider.)

A tubular prolongation of the posterior end of the œsophagus which passes through the proventriculus and opens at various positions in the anterior part of the chylific stomach. (Gehuchten.)

Œsophagus. - A small tube of the digestive system commencing at the posterior end of the buccal cavity, passing upwards and backwards directly under the brain, and merging into the crop or proventriculus, either at the back part of the head or in the thorax. (Gr. oiso, to carry, and phago, to eat).

Olfactory. - Pertaining to, or, used in smell. (L. oleo, to smell, and facio, to make.)

Olfactory nerve centres. - Paired swellings constituting the deutocerebron.

Olivaceous. - Olive green, resembling the green colour of olives. (Gr. elaia, an olive.)

Ommateum. - The compound eye. (Gr. ommatos, the eye.)

Ommatidia. - The eye elements, those parts of the eye constituting its structure. (Boas.) (Gr. ommatoo, to furnish with eyes.)

Onischiform. - Shaped like an Oniscus or Wood Louse. (Onischus, a wood louse, and form.)

Onyches. - Claws, the movable hooks usually situated at the tip of the tarsi. (From Gr. onyx, the nail.)

Onychia. - Foot-pads. (Gr. onyx.) See Pulvilli.

Onychium. - The last joint of the tarsus which carry the onychia or onyches. (Gr. onyx.)

Ootheca. - The egg-envelope, or egg case; the membrane exuded by the female during oviposition, and with which she covers the deposited eggs. (Gr. oon, an egg, and theca, a case.)

Oothecal membrane. - [See Ootheca.]

Oothecal plates. - Two chitinous plates situated at the external orifice, within the lower lip, of the cloacal chamber, and exercised by the female while laying her eggs, to cut the oothecal membrane.

Opacus. - Clouded, not transparent. (L. dark.)

Opalino. - (Splendour.) Of a bluish-white, reflecting prismatic colours. Like the splendour of opals. (L. opal.)

Opalizans. - Opaline. - (L. opal.)

Opercula. - The covering of the spiracles of the metathorax. (L. operculum, a lid or cover, from operio, to cover.)

Operculiform. - Having the shape or form of a lid or cover. (L. operculum, and forma.)

Operculum. - A lid; a small valvular appendage. (L.)

Ophthalmothecæ. - The eye-cases, that portion of the theca enclosing the eyes. (Gr. ophthalmos, the eye, and theca, a case.)

Optic ganglia. - The two nerve centres from which the optic nerves arise, each is formed of a series of ganglionic masses situated between the compound eyes and the procerebral mass, - the ganglionic plate, external medullary mass, and the internal medullary mass. (Gr. optikos, and ganglion.)

Optic nerve. - The nerve of the eye, which conveys the impressions of vision to the cerebral ganglion, and which is formed by the fibres of the internal medullary mass, and the procerebrum uniting. (Fr. optique, from Gr. optikos, pertaining to sight, and neuron, a cord.) See Nervi oculorum.

Optic tract, or trunk. - The optic nerve. (Fr. optique, and L. traho, tractum, to draw; or truncus.)

Opticon. - The first swelling of the optic tract. (Gr. optikos.)

Ora. - The broad lateral margin of the prothorax. (L., edge, cable, etc.)

Orb. - A globe; a circle. (L. orbis, a circle.)

Orbicular. - In the form of an orb. (L. orbicularis, from orbis.)

Orbiculate. - A depressed globe in form, whose horizontal section is circular, and vertical oval; being in the form of an orb. (L. orbiculatus, from orbis.)

Orbital. - Relating to the upper border of the eye. (L. orbis, and eo, to go.)

Ordinate. - When spots, puncta, etc., are placed in rows. Thus the terms ordinato-punctate, etc., are constructed. (L. ordinatus, in order.)

Orichalceous. - Resembling gold in colour. A splendour intermediate between that of gold and brass. (Gr. oros, a mountain; and chalkos, brass.)

Orthoptera. - A family of Hexapoda. An order of insects having four wings, the first pair being leathery with longitudinal veins, and the second pair fan-shaped. (Gr. orthos, straight, and pteron, a wing.)

Os. - A mouth; a bone. (L.)

Os hyoideum. - The tongue bone, the horny portion of the lingula, which often protrudes beyond the anterior margin of the mentum. (L. os, and Gr. uoides, “a bone on the top of the windpipe, shaped like the letter U.”)

Osmeterium. - The large coloured V-shaped fleshy process, which the caterpillars of the swallow-tailed butterflies protrude from a transverse slit on the dorsal surface of the prothoracic segment.

Osseous. - Resembling bone; bony. (L. osseus, from os, ossis, a bone.)

Ostia. - Lateral slit-like openings, along the sides of the “heart.” (L. ostium, a door, entrance.)

Outer. - Being on the outside; external; opposed to inner. (M.E. utter, a comparative form of ut, out.)

Outer edge. - (Wing.) The extreme border running from the apex to the inner angle.

Ova lavosa. - Eggs which are placed in closed cells formed by the parents for the reception of the ova; for ex. Apis, Vespa. (L. ova, eggs, and favus, honeycomb.)

Ova gallata. - Eggs which are placed in the galls of plants; for ex. Cynips, Diplolepis. (L. ova, eggs, and galla, a gall-nut.)

Ova glebata. - Eggs which are concealed in lumps of dung; for ex. Gymnopl pilularius. (L. ova, and gleba, a clod, soil, etc.)

Ova gummosa. - Eggs which adhere owing to the presence of a gummy secretion. (L. ova, and gummis, gum.)

Ova imposita. - Eggs which are deposited within the food of the young; for ex. the eggs of Ichneumons in the bodies of larvæ. (L. ova, and impositus, part. of impono, to lay, set, or place in.)

Ova nuda. - Eggs which lie dispersed in any direction; for ex. the eggs of Musca domestica L. (L. ova, and nudus, naked, disclosed.)

Ova pilosa. - Eggs deposited in irregular heaps over which the female spreads hair from her posterior abdominal segments to secure them from adverse elements; for ex. the eggs of Anisopteryx aescularia L. (L. ova, and pilosus, hairy.)

Ova solitaria. - Eggs which are placed singly upon the food plant; for ex. the eggs of Sphinx convolvuli L. (L. ova, and solitarius, solitary.)

Ova spiraliter deposita. - Eggs which are placed in a spiral line around the young shoots of the food plant; for ex. the eggs of Clissiocampa neustria L. (L. ova, spiral, and depositus, from depano, to lay.)

Oval, Ovate, Ovoid. - Of the shape of an egg, elliptical. (L. ovum, an egg.)

Ovaliform. - Having the longitudinal section oval, and the transverse circular; in the form of an oval. (L. ovum, and form; ovi-form, egg-shaped.)

Ovarian tubules. - The ovarioles. (L. ova, and tubula, tubes.)

Ovaries. - Part of the female genitalia. They are a pair, consisting of a varying number of tubules (ovarioles) which usually extend like fingers from the anterior end of the oviduct. Each ovariole is surrounded by a thin membrane and is immature anteriorly, consisting of small homogeneous cells; further back there are larger cells, young ova, lying in the middle of the tube, and surrounded by smaller cells, which provide them with nutriment, and also secrete the shell (chorion), for the fully developed egg. (Der, ov-ar-y; Late L. ouaria, that part of the body in which the eggs are formed.)

Ovarioles. - Tubes or tubules which carry the ovaries. [See Ovaries.]

Ovate. - Egg-shaped. (L. ova.)

Oviduct. - The tube formed by the eight tubules of the ovary. Two in number. (L. ovum and duct.)

Ovigerous. - The term applied to a female insect after copulation and the first moult after copulation has taken place. (L. ovi, and gero, to bear.)

Oviparous. - Producing eggs. (Oviparous, ovi-parous, from L. oui-parous, egg-producing.)

Oviposition. - The laying of eggs. (L. ovum, and pono, to place.)

Ovipositor. - An appendage of the telum whereby the female insect lays her eggs. The ovipositors of insects vary, they may be external, as in the Ichneumon; or tubular retractile, as in the bot-flies, or saw-like (terebella). (L. ovi, and positor, from pono, to lay down.)

Ovisac. - The cavity in the ovary which holds the eggs. (Coccidæ.) The envelope in which the eggs are laid; sometimes spoken of as sac. (L. ovum, and sac; A.S. sacc - L. saccus, a bag.)

Ovi-viviparous, or ovo-viviparous. - Producing living young, i.e., the egg is hatched in the mother, and the young thus born are well developed; a species of propagation to which the ancients applied the name Insecta ovo-vivipara. (L. ovum, and viviparous, from L. uiui-parous, producing living young. - L. vivus, living; parere, to produce.)

Ovoid, Ovoidal. - Egg-like; egg-like in shape. (L. ovum, and Gr. eidos, like.)

Ovum (ova). - The egg; the bodies in the ovaries which, when impregnated, become the embryos. (L.)