what are the thins that sell for good money that the crawlers drop, like some sort of calculi or thread or something, anyways I'm not really sure so please tell.
Most crawlers only drop Silk Thread. The ones in East and West Sarutabaruta drop the Crawler Calculus and also Smooth Stones, both of which are quest items.
The Crawler Calculi can be turned in for a repeatable quest, 3 calculi for 600 gil.