Sorry to be revisiting an old post, but I had a quick question. Hopefully somebody sees this. Do soldier fly larvae need a substrate, or can one simply throw food scraps in? I found a piece of rotting and molding piece of fruit the other day, and noticed it was getting kind of stinky, and I think it's because of the substrate. Any advice as to what I could use for fresh substrate for the larvae to crawl around and burrow in?