Nasty long LEGS!

I'm being menaced by a cranefly! I know they can't hurt me... But when I glance up and see a cranefly in extreme close-up, flying directly at my face... and I jump up, squeaking, and can no longer see it... Is it down my shirt? In my hair? In my mouth? And I have just settled down again, fingers poised to resume writing... when it starts on another circuit of the room and the whole thing is repeated all over again.

Why is it that flying and/or scuttling things with longs legs are so scary, even when our rational mind tells us that they can't do a thing to hurt us?