In order to grow larger, a tarantula must molt every once in awhile. There are usually a few ways to tell if your spider is about to molt.  For one it probably won’t eat for a few weeks before the big moment, and they usually develop a bald spot on their abdomen which will turn purple at the last minute. 

If you see your spider on it’s back, it is imperative that you do not disturb it.  If it is stressed out, it could get stuck in the old skin and die.  Also make sure that there are no live prey left in the cage, as a hungry cricket may nibble on a tarantula, causing injury. 

It may take a few hours for your tarantula to finish the process, and you should wait a few days to remove the old skin. After a tarantula molts, it’s skin and fangs are still soft, leaving the spider vulnerable.

When they are approaching a molt, make sure the humidity is optimal. If the cage is too dry, they may get stuck in their old skin and die.