If it is a light colored ooth as from a Gongy, you might be able to see the little partially formed nymphs if you hold it up to a strong light and use a jeweler's loop (7-10X). I know that won;t work with darker ooths like Ghosts and Creos. It is how egg ranchers to it. They call it candling. Time is the best, if given the right conditions. After several months though, if it is something you need to know, you can tehn cut it. Perhaps only cutting off one end and allowing the other end to be virile still. Then if the peek shows that it is fertile, you have not ruined the entire ooth. There will still be some nymphs possibly that have not been dessicated, there to hatch.