The Wild Silkworm from the beta was actually a quest mob/item or something like that. It was removed and I don't think they'll be adding it back.
In patch 5.1 there will be a new pet, Imperial Silkworm, that will use the same model as the Jungle Grub except it will be a red/pink version.
Feel free to browse through Perks N Peeves
, my vanity pet collecting blog!