harvestman vs arachnid

harvestman and arachnid both are nouns.

Word	Noun	Adjective	Verb	Adverb
harvestman	Yes	No	No	No
arachnid	Yes	No	No	No

As nouns, arachnid is a hypernym of harvestman; that is, arachnid is a word with a broader meaning than harvestman:

harvestman: spiderlike arachnid with a small rounded body and very long thin legs
arachnid: air-breathing arthropods characterized by simple eyes and four pairs of legs

Other hypernyms of harvestman include arachnoid.

harvestman (noun)	arachnid (noun)
spiderlike arachnid with a small rounded body and very long thin legs	air-breathing arthropods characterized by simple eyes and four pairs of legs