It seems like a little late to be responding to your July post, but better late than never? The 'simple' (yeah, right) solution to your problem with predation is to bring them indoors. Stink bugs, ants, spiders, grasshoppers, all take their toll on caterpillar numbers. We brought the eggs and very early instars, indoors last summer and while it was a HUGE amount of work, it was very successful and well worth the effort. I wrote many posts about our experience so I won't repeat here...if you're interested, click my profile and then "all posts by this member" and sort through them. As much work as it was, we're gearing up for this summer's 'production.'
Waystation # 850