leaf bug vs hemipteron

leaf bug and hemipteron both are nouns.

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

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

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

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

leaf bug (noun)	hemipteron (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