The Facehugger is the most terrifying of the Xeno life cycle because of anticipation. If you get one on your face and wake up you know you're going to die horribly. The Chestburster is dyad with facehugger, the Facehugger is more terrifying because you know its impregnating you with a chestburster.
There is a Spider in Australia that comes close to the Facehugger in size and color called The Huntsman Spider.