Japanese beetle vs Popillia japonica

Japanese beetle and Popillia japonica both are nouns.

Word	Noun	Adjective	Verb	Adverb
Japanese beetle	Yes	No	No	No
Popillia japonica	Yes	No	No	No

As nouns, Japanese beetle and Popillia japonica are synonyms defined as:

Japanese beetle and Popillia japonica: small metallic green and brown beetle native to eastern Asia; serious plant pest in North America

Japanese beetle (noun)	Popillia japonica (noun)
small metallic green and brown beetle native to eastern Asia; serious plant pest in North America	small metallic green and brown beetle native to eastern Asia; serious plant pest in North America