crab louse vs sucking louse

crab louse and sucking louse both are nouns.

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

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

crab louse: a louse that infests the pubic region of the human body
sucking louse: wingless usually flattened bloodsucking insect parasitic on warm-blooded animals

Other hypernyms of crab louse include louse.

crab louse (noun)	sucking louse (noun)
a louse that infests the pubic region of the human body	wingless usually flattened bloodsucking insect parasitic on warm-blooded animals