I agree. I don't believe it's actually possible. They just aren't viable. With how many people do spiderXspider and get all good eggs, I don't think they exclusive die in the egg or become slugs. I think some times they can also fail to develop from conception in the mom. I think combo disrupts the DNA so much that no matter how far it makes it in development, it will never thrive. I'd like to see the average eggs laid by spider female that were bred to spiders vs the number they laid with non spiders to see if she lays fewer eggs.