Mysterious pile flattening
I built a new wooden bin last weekend, intending to move the contents of a plastic bin there. My old bin had been an outside bin during the summer and fall, mostly getting the greens that I picked like weeds and thinning crops. I stopped feeding it in October and moved it inside. I figured that it had been plenty long enough to harvest and transfer my worms to the new bin.
Like every other time I've harvested, I emptied the contents onto a tarp under a bright light. I mounded three piles and left them over night. The next morning I came down and looked at a completely flat surface. All three of my mounds had been reduced to an even 3-4 inches of worm poo. I struggled to figure out the cause, wondering if one of my children had come into my grow room and played with the "dirt", but I doubted that. The name of my grow room is "the room we may not enter" and they have never gone into my sanctuary before. I shrugged, scooped up the top crust and re-mounded.
When I returned home from work, the same phenomena had occurred. My mounds were reduced to flatness. This time I decided to figure out the cause. After scooping the top, I re-mounded and sat down to watch for a while.
After about a minute, my piles began to move as if tine corpses were digging themselves out of the worm poo. Zombie Worms?
I waited, then got closer to inspect and noticed that my material was filled with tiny maggots, about a tenth of an inch in size; hundreds, thousands of them. I also started noticing the pillbugs, then the light went on inside my head.
Black Soldier Flies. I had seen the adults in my grow room for several months. I experimented with dwarf tomatoes in the fall and started my onions and shallots on Jan 1st, so my grow lamps had been on for months and the room was a constant 75 degrees; the plastic bin had holes for air flow and the flies found a nice home to lay their eggs. The little maggots were so active they literally reduced my piles to a flat surface. I had never seen that before.
On the downside, my worm population was small, only about 1/4 pound. I think the BSF life cycle was consuming too much of the compost and the worms did not compete well. I'm glad I have other bins with healthy squirms.