We received this photograph from one of our readers:
She explained that she found plenty of these black creatures on her balcony, and a few of them even ventured into her house. Also, she has a composting pot on the balcony. She asked us: What kind of “worm” is this? Do they climb up beds, sofas, etc? Are they harmful?
We instantly recognize this specimen as a black soldier fly larva. Black soldier fly larvae, or BSFL for short, are the larvae of a common and widespread fly. The larvae are associated with composting because they excel at breaking down organic substrates and returning nutrients to the environment. In fact, they have such a big appetite for food scarps and agricultural waste that some people purchase them or create black soldier fly larva farms to have a supply at the ready. Our reader is lucky to have these larvae in her compost bin!
Now, on to her second question: Are they harmful? Unlike some other fly species, black soldier flies and their larvae are not considered pests or vector species. This means that they don’t carry or transmit any human diseases. So why are these creatures entering her home? We can’t say. Since they eat organic waste, they probably won’t crawl up sofas or beds. The room they are most likely to inhabit is the kitchen, specifically near the trash. Our reader should make sure her trash bins are clean and scrap-free. If our reader is anxious to get rid of these pests, she should move her compost bin farther from the entryway into her home, or keep her door closed whenever possible.
To sum up, one of our readers found black “worms” coming from her compost pot on her balcony. These “worms” are black soldier fly larvae. They are fabulous decomposers and are associated with composting. They may be unsightly, but they are doing great work in her compost bin and are not harmful to humans!