Want an easy (and free) way to feed your hens? Have you heard of black soldier fly larvae? Not sure what the big deal is? In this article, I’ll show you how we raise these insects on our farm – and why they’re such a valuable food source for your flock. You’ll also get our free plans for building your own black soldier fly larvae farm.
What Are Black Soldier Fly Larvae?
Black soldier fly larvae are the juvenile state of the black soldier fly (Hermetia illucens). The adults look a little like wasps, and the larvae might remind you of mealworms. But don’t confuse them – black soldier fly larvae and mealworms are different species, with different advantages for backyard chickens and ducks.
Since they can be found all over the U.S., particularly in southern states, you probably already have these black soldier fly larvae in your backyard! Don’t worry if you’ve never spotted them. The flies are easy to miss. We never realized they inhabited our farm until I left some horse grain in the bed of our truck during a rainstorm. A few days later, hundreds of larvae crawled out of the grain. We accidentally raised them in our truck bed! Yes, it was very gross, and it made me realize just how easy these insects are to cultivate. We had some very happy chickens that day.
Black soldier flies are everywhere. You just need to create an inviting area for the adults to lay their eggs to start your own black soldier fly larvae farm.
How Do I Feed Them to Chickens?
You may be wondering why these insects are so healthy for fowl. While the adults aren’t generally fed to chickens, their larvae make an exciting, nutritious, and free supplement in your flock’s diet. Black soldier fly larvae are about 50 percent protein and a rich source of vital nutrients, such as calcium. Since protein is necessary for feather growth and egg production, it’s clear how beneficial these yummy treats are for hens. The extra calcium will help your flock lay better eggs, too.
There’s no exact percentage for how much of your flock’s diet is replaceable with black soldier fly larvae. Just make sure that your chickens are getting all the nutrients they need. You can start by replacing 10 percent of your flock’s regular grain, and increase from there. They’ll thank you! It’s always a good idea to consult your veterinarian as well.
To feed these insects to your flock, you have some options. You can:
- Feed the insects live
- Sacrifice the larvae by freezing them (thaw them before feeding)
- Dry the larvae for long-term storage
Each option has advantages. Feeding live insects is exciting and fun for your chickens because it lets them indulge in their natural behaviors. Our birds are omnivores; they evolved to forage and seek out tasty insects. Since we keep them cooped all day, they get a bit bored! Live insects break up the monotony and give your flock a bit of exercise.
Eventually, live black soldier fly larvae will pupate into adults. The mature black soldier flies will stop breeding as summer fades to fall, and you’ll have no more larvae to harvest until the following spring. If you don’t harvest and store some of the young, your steady supply will eventually dwindle.
Feeding dead black soldier fly larvae makes it easy to mix them with feed. (Here’s a recipe you can replicate at home.) It’s also easier to hold onto dead larvae for longer-term storage (either by freezing them or drying them). If you don’t want to keep the black soldier fly larvae in your freezer, you can dry them after they’ve died in the freezer. Use a solar oven or even a household oven to dry them for long-term storage. Another method to dry black soldier fly larvae is to microwave them, however, I’ve never personally tried that method.
Plans For A DIY Black Soldier Fly Farm
Now that you know why these insects are so healthy for your hens, let’s talk about how you can raise them yourself! First, you’ll need a home for your larvae, and one way to do that is to build your own.
Building your own black soldier fly larvae farm takes just a few minutes. And it doesn’t need to cost an arm and a leg. We spent less than $20 on this project and were able to upcycle scrap wood and spent shavings from our coop to complete it.
To make this project easy and accessible for chicken keepers of all levels, we used a 55-gallon plastic bin. You can buy these at any big-box store. While plastic may not be for everyone, we wanted to show how this project can be easy, accessible, and low-cost.
If plastic isn’t your thing, then you can also build bins out of wood using this same design. It’ll cost you a bit more than just a plastic bin, but it’ll last longer. If you’re not sure that raising black soldier fly larvae is for you, then stick with a plastic bin. You’ll be less financially invested in the project, and you can always upgrade to a wood bin later.
Ultimately, the goal is to cultivate a protein-rich feed for your chickens. Since the design works well with many different types of material, feel free to use wood, cement, cinder blocks, or anything else you have on hand.
For this project, you’ll need:
- Cinder blocks, or another way to raise the bin ($1 each)
- A 55-gallon plastic bin and a smaller plastic bin ($14 total)
- A drill with a small-circumference bit (1/4-inch is best)
- Bedding substrate (free)
- Starter feed (such as ground corn, spent fruit and vegetables, horse feed, rice bran, etc).
- Corrugated cardboard (free from post office)
- 2 pieces of wood at least 6 inches wide (wider is better) and half the length of your bin (free)
Total cost: $18
Step 1: Stack your cinder blocks and bin.
Assembling your bin is easy. First, drill a few holes into the bin for drainage, so its contents won’t become waterlogged. Next, stack your cinder blocks so the bin is raised off the ground. This is important for two reasons: First, it keeps mice and rats out of your bin. Second, it creates good circulation around your bin. You don’t want the interior getting too hot, because it’ll rot the food faster (attracting the wrong kind of insects). Additionally, if your bin gets too hot, it’ll cause your black soldier fly larvae to crawl off sooner. They’ll be smaller and less nutritious for your chickens.
If you have another way to raise your bin, such as an extra table or sawhorses, you can use that instead of cinder blocks. The idea is to just get your bin off the ground.
Step 2: Add your bedding substrate to the bin.
We used spent shavings from our chicken coop. We didn’t want the interior of our bin to get too wet. A moist, anaerobic environment rots food quickly, and attracts houseflies instead of black soldier fly larvae. Some other bedding options are newspaper, wood chips, compost, or dirt.
Step 3: Add your starter feed.
We used rice bran for this project, and just dumped it on top of the shavings. We then wet the bran a little so it made a scent to attract the female black soldier flies.
Step 4: Top it off with the cardboard.
Just place the cardboard on top of the feed. The black soldier fly ladies will know what to do!
Step 5: Add the wood planks.
Place these into the bin, and lean them side-by-side against one side of the bin so they’re on a shallow slope (at least, as shallow as your bin allows). The idea is that these planks provide an easy way for your larvae to crawl out of the bin. You still will likely have some larvae crawl up the sides of your bin, but most will use the path of least resistance. If you notice a lot of the larvae crawling up the sides, you can catch the larvae by putting additional smaller bins below those areas as well. You can also add a lid to your bin to help contain and protect the larvae and their environment.
If you have strong winds like we do on our farm, weighing down the lid with a cinder block will prevent the lid from getting lost. This is especially important in storms, since you don’t want a lot of water in your bin. Excessive moisture can drown your grubs, cause them to crawl off too early, or attract the wrong kind of insects.
Step 6: Place your extra bin right below the wood planks.
Keep it as close to the ends of the planks as possible to ensure your larvae make it into the receiving bin. If you need to raise your receiving bin, just use extra cinder blocks, or something similar. Check your smaller bin daily! Adult black soldier flies only live about 7 days. In that time, they need to mate and lay eggs. Eggs take about 4 days to hatch, so you should see results quickly.
Step 7: Choose a location for your bin.
You don’t want the interior of your bin to get too hot, too moist, or too wet. If any of these conditions aren’t ideal, it can result in faster crawl-off and possible death. While the goal is to harvest the larvae to feed our chickens, you don’t want them dying too soon in your bin or crawling off before they’re large and nutritious for your birds. Choose a spot that’s in partial shade, and can keep your bin reasonably dry. Building your larvae farm in a bin lets you move it easily if it’s necessary.
Whenever we decide to set out a new bin, I look for a spot where I’ve seen larvae in the past. For example, our horses are masters at dropping their grain and mashing it into the mud. If we dig an inch or so with our boot heels and see black soldier fly larvae, we know it’s a great place to put a new bin. The flies are already attracted to that area! You can also place your bin close to your coop. Black soldier flies are attracted to the smell of chicken feed, so they’re likely already in that area.
Maintaining Your Bin and Attracting Black Soldier Flies
Now that your bin is complete, it’s on to the next step!
Your goal is to attract mature female black soldier flies and encourage them to lay eggs in your bin. These insects naturally lay eggs close to their food source. However, unlike houseflies, which lay their eggs on their food, black soldier flies lay their eggs near their food. So providing an attractive laying location, such as corrugated cardboard, is important. Any cardboard will do, although I personally would stay away from anything with a lot of ink and printing on it.
As for food, we use ground corn, rice bran, and wheat in our bins. We already have it available, and it’s less likely to attract houseflies. We also provide leftover fruit rinds, vegetables, and other kitchen waste. Experts recommend avoiding putting meat in your bin. As the meat decays, it sends off a rotting smell, which is more likely to attract houseflies. We personally don’t like the smell, so we just stick to grains, fruits, and vegetables. We’ve always had great luck with grains in particular!
Add food as needed, and keep an eye on the amount of food in your bin. If you notice it’s gone on a daily basis, add more. If there’s plenty of uneaten food in it, then hold off on adding more. While you’ll want to use leftovers from your kitchen instead of using very fresh produce, you also don’t want rotting food to create an anaerobic environment in your bin. It’ll attract maggots instead of black soldier fly larvae. It’s a balancing act, but you’ll soon get the hang of it.
How to Harvest Black Soldier Fly Larvae
As they mature, black soldier fly larvae will increase in size until they’re black and about 1 inch long. At this point, they’ll start to crawl off and out of their bin in order to move on to the next phase of their lives. Because they naturally will leave the bin, it’s very easy to harvest them. Simply wait for them to crawl off!
The planks of wood give them an easy way to leave their nest. As they crawl, they’ll eventually reach the end of the planks, and plop into the receiving bin below. You can check the bin every day for new larvae. You can then decide whether to feed them to your flock immediately or sacrifice them by freezing them.
Raising and harvesting black soldier fly larvae is relatively easy, and over time, it can provide a healthy and free source of food for your chickens.
Maat van Uitert is the founder of the backyard chicken and duck blog, Pampered Chicken Mama, which reaches approximately 20 million backyard poultry enthusiasts every month. She’s also the founder of the Living the Good Life with Backyard Chickens store, which carries nesting herbs, feed, and treats for chickens and ducks. You can catch up with Maat on Facebook and Instagram.