Making a beeline

I have attempted to make a raised asparagus bed in the corner of my garden. As I have a container garden I have little to none digable soil. So improvise wherever I can. I also have a very large water butt that I use for soaking dried out baskets etc. Over the winter it had become a bit dank with about 4" of soil deposit at the bottom. I slung this all on but was amazed to have attracted a swarm of what looked like honey bees. They were having a feast. What do you think they were?