Black Soldier Flies and Composting

Did you ever wonder what those big bugs lazily flying around compost piles were?  They are Black Soldier flies.  These flies actually look like wasps.  They have two clear spots on their abdomens that mimic the thread waist of a wasp.  This is to help protect them from predators. 


The first step in the lifecycle of a black soldier fly is the egg.  The adults lay approximately 600 eggs, no bigger than a grain of rice, in small cavities.  Depending on conditions the eggs can take anywhere from 4 days to a week to hatch. 

Once the eggs hatch, the larvae then go through six instars.  These instars are molts where they shed their exoskeleton so that they can continue to grow. 

The last of these instars is a prepupal stage.  In this stage the larvae sclerotize, they become dark in coloration and their bodies become harder.  It is at this point that the prepupa black soldier fly will seek out a dark dry place in preparation for the next stage.      

Next they pupate.  This stage is when the larvae enters a pupa.  A pupa is similar to the chrysalis of a butterfly.  Once inside the pupa, the black soldier fly undergoes a complete metamorphosis, where it changes from the larvae into the adult fly.

Finally, the last stage of the black soldier fly is the adult.  As adults they do not feed, they simply take up water.  Therefore, black soldier flies do not bite.  They typically live for up to two weeks.  Their sole purpose as adults is to perpetuate the species. 


Now that you know a bit about their lifecycle, I bet you are wondering how they can help.  These flies are amazing composters.  They are voracious eaters as larvae and 1,000 larvae can eat through 2.2 pounds or 1 kilogram of kitchen scraps a week. 

Furthermore, they will eat almost anything; kitchen scraps, coffee grounds, meat, and manure.  However, there are a couple of things that black soldier flies will not eat.  Such as eggshells, bones, or dry fibrous materials (that consists of things like weeds, grass, leaves, stalks, paper, wood, and cardboard)

Black soldier flies are native to the United States and found throughout the Western Hemisphere.  Therefore, they can be released into the area to propagate without cause to worry about releasing an invasive species. 

Additionally, Black soldier flies are temperature sensitive.  They like warm temperatures and do not tolerate cold well.  However, the larvae are able to withstand colder temperatures than the adults and strong, healthy larvae are more inclined to make it through the winter months than malnourished larvae. 

On a final note, black soldier flies are an extremely beneficial resource to help reduce landfill waste.  You can purchase black soldier fly larvae here as well and start being part of the solution to the problem! 

Author: Cassandra Ference

Frontier Agricultural Sciences


Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart