bed bug vs hemipterous insect

bed bug and hemipterous insect both are nouns.

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

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

bed bug: bug of temperate regions that infests especially beds and feeds on human blood
hemipterous insect: insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis

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

bed bug (noun)	hemipterous insect (noun)
bug of temperate regions that infests especially beds and feeds on human blood	insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis