Here's one thing I've never fully understood. If Naraku was created by Onigumo being possessed/devoured by multitudes of demons, possessing the body of a Daimyo, why does he always take the shape/ or is known as a Spider? Couldn't he just have easily taken the shape of a pissed off crane/scorpion/add-own-species-here? Just wondering.

I don't know that it was ever really explained in the manga. I know there were a couple of episodes toward the end of the main series that went into a greater detail about when Inuyasha and Kikyou met, and it showed a spider demon that was one of the ones to join with Onigumo. It kind of suggested the idea that it was a dominant personality among all of the others, so that could be a reason why Naraku is known as a spider and has the spider scar on his back. I'm pretty sure those episodes were fillers, so I don't know if they should be considered a real explanation.

I don't know why, but maybe it could be a stylistic thing, you know, a symbol by which you can easily identify the bad guy. After all, Onigumo literally means "demon spider".

lol maybe the creator is afriad of spiders and chose the spider as a symbol of fear?

I am totally terrified of spiders so I agree with Kat XD

I would have to agree with CW on this, I remember those episodes as well. Again it wasn't really explained, but CW explanation does make sense!!