Stemma

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For information regarding Stemma in textual analysis, see Stemmatics

A stemma (plural stemmata) is a simple eye which is only capable of detecting light. Stemmata do not focus and are unable to perceive images.

Stemmata are located on the sides of the head of many insect larvae. They are also called lateral ocellus. Caterpillars have six ocelli on each side of their cranium, while others such as the nicrophorine larvae bear only a single stemma on each side of the head.

As the larvae develops and matures into an adult insect, the stemmata develop into a more complex visual organ, such as the compound eye.

Most adult insects have a single pair of compound eyes. In some cases the stemmata continue to function, becoming an internal component of the adult insects more advancedly developed visual organs.