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 Class 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.