In the trailer of Silent Hill (1999), I found a beta version of the Larval Stalkers. They look solid like a body rather than ghost-like. In the final, they were now ghost-like appearance. The reason why is they were to much like children (same way as Grey Children as they were replaced by Mumblers in Europe and Japanese version), so they make them like ghosts and cannot be killed. At 1:32 and 1:38.