Yeah... you really didn't know a lot about how some wasps and such work, did you?
There's all kinds of horrifying parasitoids out there. I think wikipedia has a list of some interesting ones. It involves cockroach zombies!
http://en.wikipedia.org/wiki/Emerald_cockroach_wasp(Freaky things, some wasps. Some kinds have become symbiotic with a virus. They all have it (it's permanently in thier DNA), and it messes with rejection responses in other creatures. Some kinds (including this) have specialized stings and techniques to modify brain function in other creatures. A LOT of them (and all of the aforementioned) have parasitoid young. Brrrr...
http://en.wikipedia.org/wiki/Parasitoidhttp://en.wikipedia.org/wiki/Parasitoid_wasphttp://en.wikipedia.org/wiki/Category:Mind-altering_parasitismNote that the last includes human entries.
Pleasant nightmares.
Funny... I can't find any mention of parasitoid spider larvae, just wasps...barnicles...fungi, things like that. Spiders are definitely creepy and alien enough for it though...
It's kind of scary to know how much horrifying/perverted/wierd/just plain
alien stuff you see in movies/etc. is actually based on nature...
Earth is a varied and terrifying planet. Just ask the Austrailians...
EDIT: My point being: anything spiders can do in the field of freaking-people-out-with-your-gross-biology, wasps can do better (Except that web stuff. Few use it, and they have to brainwash spiders to do it!). And the legs. Eight just looks... even more WRONG than six. Ditto with the eyes. OK, spiders are pretty freaky. Actually, they are scarier than wasps, I just can't understand why, as wasp biology inspires more sci-fi horror than spiders do...
Documentry vid on that wasp:
http://educatedearth.org/video.php?id=5215