Cycling with Black Soldier Flies

Photo: (Courtesy of Sukarman)

Flies get a bum rap. We swat them. We set out traps. They get no respect. But, it’s time all that changes. Few of us acknowledge that flies, behind bees and few wasps, are amongst the most prolific pollinators in nature. Rarely, do we discuss how flies are avid recyclers, clever scavengers, and excellent monitors of plant pests. Most of the time it’s just splat with the swatter and on with (our) life.

Perhaps permaculture is the means by which flies can become recognized not just as a tolerable part of the ecosystem but actually as a component that can be extremely useful within our integrated cyclical systems. Probably the most famous and possibly beneficial of all the flies is the black soldier fly (hermetia illucens), and so it is upon this fly that our ideas will hover for a while.

Characteristics of the Black Soldier Fly

Undoubtedly, the swatting of flies has not come without reason. Some flies will deliver nasty bites. Other will feed on garbage and/or faeces then perch upon our food, effectively transmitting diseases. But, with the black soldier fly things are a bit different. While it may be an average fly in a lot ways—two wings, six legs, two antennae, the black solider fly is an upgraded version of what we normally think of as a fly.

Unlike those pesky flies, black soldier flies don’t fly well, so they spend most of their time on compost heaps and manure deposits rather than buzzing around our food or us. In fact, they don’t have mouths, so they are no big worry for biting or contaminating our food. Even better, houseflies, which can be problematic, tend to steer clear of breeding areas with black soldier flies.

Black Soldier Fly (Courtesy of harum.koh)
Black Soldier Fly (Courtesy of harum.koh)

Physically, they are also a bit off of what we think flies look like. They have trim waists between two body segments, giving them a bit of a wasp-like appearance. There wings transparent black and often resting atop their backs as they dock near animal housing. They are about two centimeters long and black with two clear rings along their lower, abdominal, body segment.

Climatically speaking, black soldier flies are into hot spots, places a little too steamy for the average earthworm. They live in tropical and subtropical areas in the Americas, as well as in Australia. They like sunny spreads with a structure or two to rest on, perhaps some vegetation around, especially some flowering daisies or carrots. A composting bin or thunderbox suits them just fine.

How Black Soldier Flies Get Into the Mix

At this point, it all sounds relatively pleasant. Black soldier flies don’t bother us—great. They deter troublesome flies from finding comfortable breeding spots—even better. And, surprise, surprise—they are black. But, do any of things warrant a round of applause or praise. How do black soldier flies make any difference to our food cycles?

Soldier Fly Egg Depository (Courtesy of Charlie Vinz)
Soldier Fly Egg Depository (Courtesy of Charlie Vinz)

To begin, the larvae of black soldier flies, which most certainly have mouths, are strong competitors in all-natural eating contests (measured by body weight to food ratio, of course). They can convert organic matter, everything from manure to mold to carrion to plant refuse. When eating it, they massively reduce the size and weight of the waste, and they do it all so quickly that nothing has time to decay and make a stink. They are magic in the compost bin.

In eating the compost, they not just create rich liquid fertilizer, which attracts more black soldier flies to lay their eggs, but they also get plump, sometimes over an inch long and quite roomy through the middle. They essentially convert the manure or organic waste into a protein-rich, fatty little larvae that other animals—fowl and fish, especially—will happily feed on. In other words, they can be fed back to the animals that are feeding them. For the experimental person, they are also edible for humans.

A third play to make with the larvae is as a deterrent for many other pests, especially the more problematic types of flies. The way that the larvae eats churns manure into something much more liquid-like and uninviting for egg-laying and larvae development of other flies. Having mild-mannered black soldier flies around can greatly reduce the number of pest flies, and in fact, they were formerly used in the American South to control fly population around outhouses and were thusly called “privy flies”.

Outhouse/Privy (Courtesy of Shawn Ford)
Outhouse/Privy (Courtesy of Shawn Ford)

Kicking Starting Your Black Soldier Fly Farm

It doesn’t take much figuring to guess that many folks out there, only now becoming aware of the black soldier fly, would be interested in introducing them onto their farming sites and finding them a fit within everyday cycles. The process isn’t so difficult, and there are loads of resources to help with (Check out this video series exclusively on black soldier fly production).

The basic requirement for farming black soldier flies is having a box for them to do their thing in. The box should have a drain hole in the bottom so that it doesn’t flood and the valuable liquid can be harvested, and the lid should have something that props it slightly ajar so that flies can come and go as they choose. Put some absorbent substrate at the bottom of the bin, such as wood shavings, shredded cardboard, or spent coffee grounds. Add some manure and whatever organic matter collected in the kitchen.

Due to the environment that black soldier fly larvae creates, not much else—save from composting worms—will be interested in living in the box. The effluent from the black larvae will keep mothers coming back and laying eggs (about 500 at a time) in the box so that the population will multiply quickly. And, then, well, you are an official black soldier fly farmer. Enjoy the benefits.

YouTube! Video: Building a Black Soldier Larvae Bin Out of Recycled Materials

Jonathon Engels

The financially unfortunate combination of travel enthusiast, freelance writer, and vegan gardener, Jonathon Engels whittled and whistled himself into a life that gives him cause to continually scribble about it. He has lived as an expat for over a decade, worked in nearly a dozen countries, and visited dozens of others in the meantime, subjecting the planet to a fiery mix of permaculture, music, and plant-based cooking. More of his work can be found at Jonathon Engels: A Life About.


  1. What if you don’t have BSFs around in your area, then how do you keep hatching new larvae? Just separate some out into another bin with bedding and food and they’ll develope into flies?

  2. I wanted to put my BSFL bin in a fruitfly excluding net tunnel. Are the adults good polinators? The tunnel is too small to sustain a native bee hive.

  3. I’m fine with them being in my compost, but they keep sneaking into my house! How do I prevent/ deter the larvae from slipping under my door? I have added a strip to the bottom of the door, but they seem to be unphased by it.

  4. What is the market place for the larvae of black soldier fly?
    (List of market places for the larvae of black soldier fly).

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