The mulberry food became popular as they became popular as a feeder insect. I really couldn't give an exact date, but it's been more than a few years. It's just dried ground mulberry leaves with a little bit of vitamins added. I've actually got three cocoons now, so I guess I shall let them hatch. Damn male beardie has decided he isn't a large fan of the silkworms any more. The geckos like them, 1 female in particular, but there are only so many those guys can eat