sucking louse vs insect

sucking louse and insect both are nouns.

Word	Noun	Adjective	Verb	Adverb
sucking louse	Yes	No	No	No
insect	Yes	No	No	No

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

sucking louse: wingless usually flattened bloodsucking insect parasitic on warm-blooded animals
insect: small air-breathing arthropod

sucking louse (noun)	insect (noun)
wingless usually flattened bloodsucking insect parasitic on warm-blooded animals	small air-breathing arthropod
	a person who has a nasty or unethical character undeserving of respect