Japanese beetle vs scarabaeid

Japanese beetle and scarabaeid both are nouns.

Word	Noun	Adjective	Verb	Adverb
Japanese beetle	Yes	No	No	No
scarabaeid	Yes	No	No	No

As nouns, scarabaeid is a hypernym of Japanese beetle; that is, scarabaeid is a word with a broader meaning than Japanese beetle:

Japanese beetle: small metallic green and brown beetle native to eastern Asia; serious plant pest in North America
scarabaeid: any of numerous species of stout-bodied beetles having heads with horny spikes

Other hypernyms of Japanese beetle include scarabaean, scarabaeid beetle.

Japanese beetle (noun)	scarabaeid (noun)
small metallic green and brown beetle native to eastern Asia; serious plant pest in North America	any of numerous species of stout-bodied beetles having heads with horny spikes