Perhaps "super" isn't the best term. It sort of implies a combination of both a phenotype (appearance) and a genotype that only really works for co-dominant/incomplete dominant mutations.

There could still be a HOMOZYGOUS spider (just like you can talk about a homozygous normal relative to a certain mutation). I'm not sure how many spiders from spider X spider breedings have been bred to test if any of them are homozygous rather than just heterozygous spider like the earlier spiders. If spider isn't lethal when homozygous then there should be a homozygous spider eventually. If it looks the same as a heterozygous spider it would still be a significant difference because you could breed a homozygous spider male to normal females and produce all spiders rather than just average 50% spiders.