ocellus vs stemma

ocellus and stemma both are nouns.

Word	Noun	Adjective	Verb	Adverb
ocellus	Yes	No	No	No
stemma	Yes	No	No	No

As nouns, ocellus and stemma are synonyms defined as:

Other synonyms of ocellus include simple eye.

ocellus (noun)	stemma (noun)
an eyelike marking (as on the wings of some butterflies); usually a spot of color inside a ring of another color	an eye having a single lens
an eye having a single lens	the hereditary derivation of an individual
	a tree diagram showing a reconstruction of the transmission of manuscripts of a literary work