Q.Draw a neat and labelled diagram of Ommatidium.

An ommatidium is the single structural/functional unit of the compound eye; thousands of them together form the compound eye of the cockroach.

Note on the figure: This question asks for a drawn, labelled diagram. A hand-drawn image cannot be produced in this text answer, so instead the structure is described part-by-part, in the same order they would be labelled top-to-bottom on a diagram, so the layout can be reconstructed and drawn accurately.

Structure of an ommatidium (outer to inner):

1. Cuticle/Corneal lens: the outermost transparent, biconvex cuticular lens that admits and focuses light.
2. Corneagen cells: a pair of cells beneath the cornea that secrete/renew the corneal lens.
3. Crystalline cone: a transparent, cone-shaped structure just beneath the cornea that further focuses light onto the light-sensitive part below; surrounded by four cone cells (Semper cells).
4. Primary (iris) pigment cells: surround the crystalline cone, optically isolating each ommatidium from its neighbours.
5. Retinula cells: a group of (typically 7-8) elongated sensory (photoreceptor) cells arranged radially around a central axis, beneath the crystalline cone.
6. Rhabdom: a central, rod-like structure formed by the fused inner (microvillar) borders of the retinula cells; it is the actual light-sensitive photoreceptive element that converts light into nerve impulses. …