plant bug vs hemipterous insect

plant bug and hemipterous insect both are nouns.

Word	Noun	Adjective	Verb	Adverb
plant bug	Yes	No	No	No
hemipterous insect	Yes	No	No	No

As nouns, hemipterous insect is a hypernym of plant bug; that is, hemipterous insect is a word with a broader meaning than plant bug:

plant bug: small bright-colored insect that feeds on plant juices
hemipterous insect: insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis

Other hypernyms of plant bug include bug, hemipteran, hemipteron.

plant bug (noun)	hemipterous insect (noun)
small bright-colored insect that feeds on plant juices	insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis