backswimmer vs hemipteron

backswimmer and hemipteron both are nouns.

Word	Noun	Adjective	Verb	Adverb
backswimmer	Yes	No	No	No
hemipteron	Yes	No	No	No

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

backswimmer: predaceous aquatic insect that swims on its back and may inflict painful bites
hemipteron: insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis

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

backswimmer (noun)	hemipteron (noun)
predaceous aquatic insect that swims on its back and may inflict painful bites	insects with sucking mouthparts and forewings thickened and leathery at the base; usually show incomplete metamorphosis