A bee in its own right has a chance of producing a bee when crossed with a normal. IMHO, since this is a possibility I will say that a bumble bee is a co-dominant which not only produces its base morph - pastels and spiders but also a bumble bee as well. Sire passes a bee gene, dam passes a normal gene. Smells co-dominant to me.

Just the same, a killer bee (aka super pastel spider) does the exact same thing.