wow, are you sure about getting that many silkworms... you do know they cocoon don't you?
there's a few different places you can get silkies from...
http://www.thewormroom.com - i know her and she's really great!
http://www.canadianfeeders.com/ - great canadian supplier
http://www.silkwormwholesale.com/ - heard great things about them.
and of course,
http://www.mulberryfarms.com
to name a few... ;)
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and yes you can feed the newly shed mealworms (which are white) but man that's a lot of work to get those guys. i was doing that for awhile but it was just too much work to dig them out and wait for them to be ready... silkworms, for me, are much easier.
i start them from eggs, feeding them and growing them to feed.