Our Friends, the Compost Maggot

Several insects thrive in decaying organic matter, so compost bins usually provide all the resources that they need. Maggots are an important part of the nutrient recycling process. Black soldier fly maggots are among the most disturbing of the “decay dwellers,” a seething blanket of them on the heap is a startling sight. However, there is no cause for concern for the maggots or the adults.

Figure 1. Black soldier fly larvae are a common sight in decaying organic matter,-including compost bins, earthworm beds, and animal waste (Photo: Lee Townsend, UK).

Figure 2. Adult black soldier flies take a little moisture but do not feed and die in a few days. They are rarely seen, even around the larval breeding material (Photo: Lee Townsend, UK).

Kits containing rearing containers and some starter “grubs” are sold online, but this insect is widespread and egg-carrying females will find and lay eggs on compost relatively quickly. The developing flat-bodied maggots consume 8 to 10 times their body mass as they develop, leaving behind a “tea” that can be used to fertilize plants. Another benefit is these insects make their breeding site too wet for house fly development. This important attribute has resulted in the species being used for filth fly management in animal manure. In some systems, the larvae are harvested and used for animal feed.

Soldier fly maggots are a normal part of the decay process and pose no threat.


By Lee Townsend, Extension Entomologist

Posted in Landscapes