true bug vs hemipteron

true bug and hemipteron both are nouns.

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

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

true bug: any of various insects of the order Hemiptera and especially of the suborder Heteroptera
hemipteron: insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis

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

true bug (noun)	hemipteron (noun)
any of various insects of the order Hemiptera and especially of the suborder Heteroptera	insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis