OK I admit I'll show by "newbie-ness" here but after planting several milkweeds, butterfly weeds, fennel and dill, all I've had to show for my initial attempts to lure butterfly/caterpillars was one hungry guy who ate all my dill in 2 days and then vanished as far as I know.

Today I went out to give my thirsty milkweeds some supplemental rain water and ... crawling on my butterfly weeds ... were not 1, not 2, but 5 monarch caterpillars! Am so excited. However, I've only got 2 mature butterfly weed plants. Is it possible they will consume them all rapidly? If I've only got 2 should I buy some more and if I can't plant them till tomorrow afternoon is that too late?

In short, anyone have any ideas on how rapidly I should expect these plants to last 5 hungry babies?