I found this..
PRO & CONS:
* The great thing about silkworms is that they only grow as much as you feed them, and they can go for up to a week without food.
* Keep in mind, however, that silkworms become dehydrated after a few days without food, and should be feed at least once daily in order to remain healthy.
* But, in general, if you have too many silkworms you can feed them a few times per week and they'll stay alive until you need them without growing too much larger.
* They are easy to mind if you need to go away.