leaf bug vs hemipterous insect

leaf bug and hemipterous insect both are nouns.

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

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

leaf 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 leaf bug include bug, hemipteran, hemipteron.

leaf 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