action of a longlegged spider rapidly bobbing up and down on the spot - usually in a corner of the ceiling.- for no apparent reason except maybe to unnerve the viewer
''eeww! look a spider''
''what the hell is it doing''?
''it's being weird..it's...it's..mandibating''
''oh god i hope it's not getting ready to leap''
''AAARRRRGGGHHHHHHHHHHHH''......runs from room.