eye, compound defined in 1951 yeareye, compound - eye, compound;
eye, compound - Eye of insects and Crustacea. Consists of a number of separate elements (ommatidia) each with light-sensitive cells and refractive system which can form an image; the ommatidia being separated from each other in varying degrees by pigment. According to the structure of the eye, and to the distribution of pigment between the ommatidia, the eye can form either apposition images, in which case each ommatidium will focus only rays almost parallel to its long axis, so that each forms an image of only a very small part of the visual field, an image of the whole resulting from combination of these part images; or superposition images in which the sense cells of an ommatidium may receive light from a large part of the visual field so that the image received may overlap those received by as many as thirty neighbouring ommatidia. The superposition image thus gains in luminosity but loses in sharpness compared with the apposition image. Diurnal insects have apposition eyes, nocturnal ones superposition, but there are many intermediate grades; and in some cases one may change temporarily into the other by movement of pigment between the ommatidia (dark adaptation).
near eye, compound in Knolik
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