Make sure that you put about 4" of potting soil in the bottom of the jar because they form their cocoon underground.

I have raised many of them, and they are fun! This time of year, they will almost always emerge in about 2-4 weeks. Also put some sticks in the jar so that when they do emerge, they can hang from the sticks to dry and expand their wings.

The caterpillars raised in August-September will likely overwinter as cocoons to emerge next spring. Altho I have seen some emerge and some overwinter.

If you overwinter some, you should keep the soil slightly damp so the cocoons don't dessicate. Also, keep the container outdoors, or in an unheated garage or basement. Otherwise, they will emerge too soon when there is no food available for them.....die, sadly.

I attached a link to Bug Guide which has some good info on raising hornworms.

Good luck with raising your caterpillars.

Susan

Here is a link that might be useful: Raising Hornworms