true bug vs hemipterous insect

true bug and hemipterous insect both are nouns.

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

As nouns, hemipterous insect is a hypernym of true bug; that is, hemipterous insect 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
hemipterous insect: insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis

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

true bug (noun)	hemipterous insect (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