of all the organs of special senes the most important are compound eyes ,which are large and sessile situated on the sorsal surgaces of the head in the form of black kidney shaped patches in insects there are 2types of eyes (a)simple eyes or ocelli,(b)compound eyes or in cockroach each eye consists of about 2,000hexagonal facets or ommatidia which are covered externally by a tranaparent cuticle called the cornea, a single ommatidium consists of (1)corneallens or facet which is formed by the transparent cuticle,(2)A pair of corneagen cills which form the corneal lens (3)A refraactive crystalline cone encloced by four elongated conical cills called cone cells or vitrellae.(4)Distal pigment cell round the cone (5)Retinual cinsisting of eight cells forming a rhbdome.(6)Basal pigmint cill around the retunula,(7)The basement membrane.
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