For information regarding Stemma in textual analysis, see Stemmatics
For "stoma" or "stomata," gas exchange pores on plant leaves, see Stoma.
A stemma (plural stemmata) is a simple eye which is capable only of detecting light. Stemmata neither focus nor allow reception of images.
Stemmata are located on the sides of the head of many insect larvae. They are also called lateral ocelli. Caterpillars have six ocelli on each side of their heads, while others such as the nicrophorine larvae have only a single ocellus on each side of their heads.
As the larva develops and matures into an adult insect, the stemmata either are replaced by a more complex visual organ, such as a compound eye, or they become an internal component of that organ.
