in taxon Vertebrata <vertebrates> stemma stemma Eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eyespot, to allow the organism to deduce the angle of incoming light. pit eye Wikipedia:Stemma UBERON:0000046 Beutel RG, Friedrich F, Yang X-K, Ge S-Q (2014) Insect Morphology and Phylogeny Insect morphology and phylogeny: a textbook for students of entomology. De Gruyter. https://doi.org/10.1515/9783110264043 "Stemmata are specific lateral eyes (the term “lateral ocelli” is inappropriate) of larvae of most groups of Holometabola. They are replaced by the adult compound eyes during the metamorphosis. The number ranges between seven and one and they are absent in different groups. Structurally, they resemble ommatidia and are suitable to perceive movements, directions and distances." uberon simple eye