One interesting thing aoubt the north pole is that there are no well defined spider shapes photographed so far. This photo is aoubt the best of the photos available.
This may be an important clue as to what forms them, that there may be something different on the two poles. For example while the south pole temperature gets around zero the north pole doesn't seem to get above -100C. This would imply whatever forms the spiders might occur between these two temperatures. CO2 sublimates lower than -100 but water, especially if salty sublimates I believe down to -60C.
It might also be that CO2 outgassing needs to be of a certain strength which only occurs over -100C.
Because of the irregular orbit the north and south poles are alternately favoured by higher temperatures, and whatever the spiders are they may be dormant on the north pole. Still it does illustrate that the spiders may tend to shrink some how in winter, not being seen clearly in current photos then. If they did cover part of the north pole then one can ask where are they now if they are made of mud, soil, etc.