I thought that Wizards constantly bear eggs and many of the formations in and around Hive lairs (fungus like growths) are actually the newly forming Thrall. The Wizards probably don't need to be fertilized because they would have offspring that are all female similar to some insects.

We know that Wizards reproduce sexually, meaning their eggs need to be fertilized. A Wizard can either mate with a male Hive (such as a Knight or even a King like Oryx) or she can actually fertilize herself. Seeing how Hive change gender rather fluidly, it makes sense that a female would still retain the organs to fertilize itself with if a mate can't be found Wormspore is some form of decomposer similar to fungus that grows on corpses in the Dreadnaught. Just dead Thrall, nothing unworthy about them except the fact that they were weak enough to be killed by others according to the Killing Logic. They probably can be eaten by the Hive since we already know Thrall pretty much pick everything clean