What are the individual units that make up compound eyes in insects called?

The individual units that make up compound eyes in insects are called ommatidia. Each ommatidium is a small, optical unit that consists of a lens and photoreceptors. These units work together to create a composite view of the environment, allowing insects to detect movement and perceive a wide field of vision.

Each ommatidium collects light from a specific part of the visual field, contributing to the overall image the insect perceives. This structure enables insects to have a very different vision system compared to other animals with simple eyes, as they can see nearly 360 degrees around them and are particularly sensitive to motion.

The other answer choices relate more generally to aspects of vision or other structures in the eye. For instance, optic lenses are components that help to focus light, but they do not refer specifically to the individual units in compound eyes. Photoreceptors are part of the ommatidia that actually detect the light, and retinae typically refer to the layer of tissue in vertebrate eyes that contain photoreceptor cells but do not pertain to the insect's eye structure.