You have a het pied right now, so breeding the spider to het pied would result in spiders and normals that are poss het pied and the only way to prove that our would be back breeding the offspring.

I second the suggestion for getting a het pied mate. If you bought any codom you would end up with that morph poss hets and normals poss hets. Any recessive morph you would get all normals het for that particular morph and poss het for the pied.