[Kalimac]

I think Tolkien did enough in the way of foreshadowing - as you mentioned, Gollum does refer to HER, and the nasty stink in the tunnel, as well as the webs, tell us that (a) whatever this is, it's probably got some animal tendencies (b) hmmm, what is it that makes *webs* again? Foreshadowing doesn't mean he has to foreshadow exactly what the menace is, only that there's a menace - and he certainly does a good job of that. (Reading that description of the tunnel seems to take about ten years, it's so well done). If we've read "The Hobbit," the precedent for unnaturally large, vicious spiders is established there. And it's hard to imagine smaller spiders coexisting with Shelob somehow - one gets the impression that she'd snap them up in an idle moment pretty easily.

Furthermore, it makes sense that the spider wouldn't be mentioned explicitly. Who would know about her? Gandalf hasn't spent much time hanging out in that part of the world ("To the east I go not"), and even Faramir, who's closest of all, knows only that Cirith Ungol is bad news. The main reason for this is that, at least going by the impression the text gives, nobody had previously had a close personal encounter with Shelob and lived to tell the tale, except of course for Gollum. Obviously she was known of before - hence the name "Cirith Ungol" - but it seems to have been one of those names like "St Martin's in the Field's" or something similar, where the name is so old that it doesn't necessarily reflect the current reality. The Orcs, of course, know that she's still there, but there's an obvious communication problem there.