crawler vs doer

crawler and doer both are nouns.

Word	Noun	Adjective	Verb	Adverb
crawler	Yes	No	No	No
doer	Yes	No	No	No

As nouns, doer is a hypernym of crawler; that is, doer is a word with a broader meaning than crawler:

Other hypernyms of crawler include actor, worker.

crawler (noun)	doer (noun)
terrestrial worm that burrows into and helps aerate soil; often surfaces when the ground is cool or wet; used as bait by anglers	a person who acts and gets things done
a person who tries to please someone in order to gain a personal advantage
a person who crawls or creeps along the ground