long-horned beetle vs longicorn

long-horned beetle and longicorn both are nouns.

Word	Noun	Adjective	Verb	Adverb
long-horned beetle	Yes	No	No	No
longicorn	Yes	No	No	No

As nouns, long-horned beetle and longicorn are synonyms defined as:

long-horned beetle and longicorn: long-bodied beetle having very long antennae

Other synonyms of long-horned beetle include longicorn beetle.

long-horned beetle (noun)	longicorn (noun)
long-bodied beetle having very long antennae	long-bodied beetle having very long antennae