Mezcal

When we went to the Riviera Maya in Mexico, we bought a bottle of Mezcal. It has been two years now and we have just been saving it as a souvenir. Well, tonight I looked at it and the worm has literally doubled in size... Is this normal? My first thought was OH MY GOD IT'S ALIVE. Then I realized how dumb that is, but I still don't understand how it happened. Does it just get bloated after a certain amount of time?