What kind of caterpillar eats milkweed leaves?

To answer this question, google Host plants by butterfly species. I found this website under this, it has lots of different pics of butterflies with lots of helpful information. I try to identify the butterflies that visit my butterfly garden, it can be very challenging. There are over 100 species in the county I live in, Cook County, near Chicago, ILL.

Try this web site http://www.dallasbutterflies.com

My facebook page is Flowers in Bloom, look for the profile pic with the gray butterfly, that's my page. I don't have any soy bean eating butterflies, but I have many pics, & pics of Monarch cats on there also.