leaf bug vs hemipteran

leaf bug and hemipteran both are nouns.

Word	Noun	Adjective	Verb	Adverb
leaf bug	Yes	No	No	No
hemipteran	Yes	No	No	No

As nouns, hemipteran is a hypernym of leaf bug; that is, hemipteran is a word with a broader meaning than leaf bug:

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

Other hypernyms of leaf bug include bug, hemipteron, hemipterous insect.

leaf bug (noun)	hemipteran (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