First, let me say that the spider story in "Gray Matter" is one of King's best stories ever. It is its own story, a piece of micro-fiction before the term was ever invented (then again, maybe I have that wrong, and that term has been around; maybe I should say flash fiction?). I've often thought it should be adapted as a dollar baby (in fact, as I write this, I maybe have an idea of a way of writing the short script, but perhaps I'll pitch that later). It literally is one of the best paragraphs King has ever written, and I wish he would try posting some paragraphs like that to his website on occasion.
Second, this intrigues me, I myself never made the connection. Can you give me the chapter where specifically the connection occurs, because I presume you mean there is a description of a web and kittens in "It." I just don't recall that, but it has been a while since I have read the book.