flea vs insect

flea and insect both are nouns.

Word	Noun	Adjective	Verb	Adverb
flea	Yes	No	No	No
insect	Yes	No	No	No

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

Other hypernyms of flea include ectoparasite, ectozoan, ectozoon, epizoan, epizoon.

flea (noun)	insect (noun)
any wingless bloodsucking parasitic insect noted for ability to leap	small air-breathing arthropod
	a person who has a nasty or unethical character undeserving of respect