excrement vs fecula

excrement and fecula both are nouns.

Word	Noun	Adjective	Verb	Adverb
excrement	Yes	No	No	No
fecula	Yes	No	No	No

As nouns, fecula is a hyponym of excrement; that is, fecula is a word with a more specific, narrower meaning than excrement:

excrement: waste matter (as urine or sweat but especially feces) discharged from the body
fecula: excreta (especially of insects)

excrement (noun)	fecula (noun)
waste matter (as urine or sweat but especially feces) discharged from the body	excreta (especially of insects)