A reader recently reached out to us after she discovered a dead rat in her hallway. When she turned on the light to get a better look at the rat she saw two brown “blobs” further down the hallway. The “blobs” were moving. She believes they are some type of larvae. She suspects that the larvae killed the rat. She wants to know how the larvae got into her house and is curious if she should be looking for a colony of these larvae somewhere in her home. Here is a photo of the “blobs” she sent us:
We believe these “blobs” are black soldier fly larvae, or BSFL for short. BSFL are usually associated with composting because they are excellent at breaking down organic substrates and returning nutrients to the environment. In other words, they eat decomposing and decaying organic material. Unlike carpet beetle larvae or pantry moth larvae, these larvae aren’t considered household pests. They also aren’t known to carry or transmit any human diseases.
In a home, black soldier fly larvae are usually found in or near a trashcan or compost bin. We think the larvae our reader found probably smelled the dead rat and were snacking on its decomposing body when our reader turned on the light. We don’t think that these larvae killed the rat, though we can’t say for certain how the rat died. We think the larvae are probably hiding out in one of her trash or compost bins. She should empty them and also scrub the entire bin just in case there is some unseen material that is serving as a food source. This should also prevent future black soldier fly larvae from hiding out in her home.
In summary, a reader noticed two brown “blobs” on her floor near a dead rat. We are confident that these organisms are black soldier fly larvae.