aphid vs louse

aphid and louse both are nouns.

Word	Noun	Adjective	Verb	Adverb
aphid	Yes	No	No	No
louse	Yes	No	No	No

As nouns, louse is a hypernym of aphid; that is, louse is a word with a broader meaning than aphid:

aphid: any of various small plant-sucking insects
louse: any of several small insects especially aphids that feed by sucking the juices from plants

Other hypernyms of aphid include plant louse.

aphid (noun)	louse (noun)
any of various small plant-sucking insects	wingless usually flattened bloodsucking insect parasitic on warm-blooded animals
	any of several small insects especially aphids that feed by sucking the juices from plants
	wingless insect with mouth parts adapted for biting; mostly parasitic on birds
	a person who has a nasty or unethical character undeserving of respect