ADDENDUM: It seems lots of folks are curious as to the mystery substance in the containers with the larvae (in addition to the frass). It is, indeed, an artificial diet of our own design. Since Monarch Watch was founded back in 1992, we have shipped hundreds of thousands of caterpillars on an artificial diet to schools an individuals as a part of our Monarch Rearing Kits. Our diet is not available at this time, but may be in the future - stay tuned!