Yes you only need a male to get 50/50 spiders/normals. Spiders are co-doms so only one parent needs to be carrying the gene that you want to be visual on the offspring. Other co-doms are pastels, lessers, mojave, cinnamons, black pastels. Those are just a few and some of the more affordable morphs. Males are also sexually mature before females.
The spider gene is a dominant gene, not co-dom.. from what I understand about the spider gene at least.