Specular Amount: use the grayscale version of the diffuse map as a base. Using the paintbrush paint the appropriate parts lighter or darker according to the greasy-looking surface of the opisthosoma's skin and the chitinous legs.
SubsurfceAmount: paint this map for the material's subsurface effect.
SubsurfaceColor: paint this map for the coloring of the subsurfaceeffect.
TransparencyAmount: paint this map for the slightly transparent legs andcephalothorax.
ReflectionColor: paint this map for the blue colored light reflections of the dark shadesof the spider's skin.
Texture Maps from Zbrush
Add the DispMaps to the material on the ShaderTree panel (Shader Tree Tab/Add Layer/Image Map),