What do black soldier fly larvae eat

Black Soldier Fly 23 May 2020

Black soldier fly larvae eat just about anything organic-based or perishable. Decaying fish, meat, animals are good protein sources for the larvae. Kitchen scraps like carrots, banana peels, zucchini, spent barley, coffee ground are also good nutrient sources. These guys do okay with fatty, oily, salty & even spicy food like Mexican or Chinese food.

Check out the baby larvae devouring a dead bird:

If you're raising black soldier fly small-scale or large-scale, look for what's available in your local area for cheap or for free. Ask local food diners if they have any food waste they're willing to give. Scraps from veggie sellers in farmer's markets are also good. They often sell rotting fish, bad fruits for cheap. Some people also get the excess food from factories or household waste.

It's okay to feed them on a plant-only diet like greens, fruits, veggies, leaves, grass, beans, etc. Some people say on this diet the pupated flies may not be as strong to reproduce though. They may grow but quite slowly. If you're raising them to treat bio-waste, maybe this is enough. For reproduction, some extra protein from fish or meat may help. The downside to these stuff is the smell.

A good moisture content for the food is around 60-70%. Some people also shred the food so it's easier for the larvae to munch on. The moisture helps make the food softer & is where the babies get their water. It helps the larvae digest the food a bit easier & faster. Make sure it's not too wet because the excess water may drown them. Overly wet substrate makes it hard to collect the larvae poop afterwards, which could be used as a good fertilizer.

What the larvae don't like

From some growers experience, the larvae don't really like the smell of onion. We guess then, they may not be into garlic or mustard. Because those stuff have a similar strong smell like onion.

In fact, we can never force the flies to eat. If they don't like the food, they'll crawl somewhere else to find better food. You'll know immediately when you see it. Like the hamburger in the video above, the larvae don't even bother touching the meat part. Which makes many viewers question if it's even real meat or just fillers. Nobody can fool the larvae.

Also, they don't seem to like fibrous (high-fiber) stuff. So coco fiber (coco coir), grass, wood chips, paper or cardboard may not be very attractive to the larvae. They can be good as bedding substrate though.

How much do BSF larvae eat

About 100 kilos of food will be good to produce 18 kilos of larvae. These guys are big eaters. In other words, 10 kilos of garbage daily is fine to raise 1 kg of larvae for about 9-15 days. In numbers count, roughly, 600,000-800,000 larvae will eat about 1 lb (0.45 kg) of food. In space count, 40 kilos of fresh manure works for 1 square meter of larvae per day.

They usually sell eggs by the grams. Let's say you buy 20 grams of eggs. Which is roughly 600,000 - 800,000 larvae as 1 egg on average weighs 25 microgram. In about 1-2 hours, they will eat up about 0.45 kilo (1 lb). So for one day we can prepare about 5-10 kilos of food for them.

They will consume like this for 9-15 days. When they've had enough & their bodies turn a bit darker, they'll automatically move themselves out. Some people soak the food in water to increase the volume & weight.

Grams of eggs Number of larvae Kilos of food per day
18 600,000-800,000 5-10

For 5- to 7-days-old larvae, their consumption rate can be about:

  • 1.3 kilos of larvae - 50 kilos of soya bean paste for 3-4 days
  • 1.3 kilos of larvae - 12.5 kilos of soya bean paste per day (about 1:10 ratio)

If the raising conditions are well enough, we can expect the yield below. Starting with 50 grams of eggs, after 2 weeks of feeding, you may end up with 200 kilos of larvae. They grow 5000x their initial body size.

Grams of eggs Kilos of larvae
18 72-75
40 166+
50 200

This is how we roughly calculate it:

Starting egg weight Weight after 2 weeks (x5000) Larvae count Total kilos
25 microgram 125,000 microgram 600,000 75

The initial egg weight on average is 25 microgram. After 2 weeks, they'll grow 5000 times bigger. So we multiply that by 5000, which gives 125,000 microgram or 0.125 grams per larvae. Then, we time that with the estimated number of larvae there is. If there's around 600,000 in the starting colony, 600,000 x 0.000125 = 75 kilos.

Please also add a margin of plus & minus depending on how many larvae survive after the eggs hatch. Also, remember these are not set-in-stone numbers. Please correct us if we got something wrong. Be flexible & observe your local environment and their re-actions when you feed your babies.

As you can see, the ratio of kilos of larvae to kilos of daily food is about 1:10. So you can imagine, if we have 4 tons of garbage to process daily, about 400 kilos of BSF larvae can help us with processing the organic waste & keep the cycle going in an efficient & sustainable manner. Truly fascinating.

Using BSF larvae to solve the trash problem in city

Also, it's good not to overfeed themselves from the start. The excess food may attract other stuff like house flies or fungi, which we do not want. You can start off with something easy like veggies, then move up to the more hardcore stuff like rotting meat.

When the larvae eat, they excrete out some pheromone. This smell "shoo" away the other insects, wasps or house flies. That's what makes them so aggressive. Sometimes you'll hear their munching sounds as they chomp down on the food. They like a bit of privacy when eating, so shade is good.

If you feed them with something that is light colored, for example oats, soya bean paste or diluted porridge, after a few days the food may change to a darker color. This is when you know the larvae are munching on the food. Then, you know it's time to feed them again.

They are really fast eaters. In 1-2 hours, they'll eat up everything. If you don't supply them in time, they'll move themselves out to some place to find food. Sometimes, they'll get noticeably skinny if you leave them hungry for a day.

Is manure good food for the larvae?

If the manure comes from a healthy animal, then it's good. You can mix them with some water to create a paste for the larvae. Chicken manure, pig manure give good results. Some find cow manure or goat dung not as effective. Because these animals eat mostly grasses, which the larvae don't find that appetizing.

Should we turn the food?

It's okay to turn the food every now & then. This helps distribute the food more evenly to everyone in the house. Don't turn it too much though. It might then be unnecessary because turning may slow down pupation & sometimes damage the larvae little bodies.  

In summary

If you want to mix a feed without an extremely unpleasant smell, try:

  • Oats/barley/bran/brewery grains
  • Fruits
  • Beans
  • Veggies

Basically, things that come from plants will give a slightly less unpleasant smell than that from an animal source (because of the high protein or nitrogen content).

In Indonesia, for example, rice bran is cheap–about $0.5-0.7 per kilo. So growers use that as food. But in Cambodia, rice bran is expensive so they choose another food source. If you live in the US, a bag of 50 lbs rolled oats can be had for about $10-20. This is very affordable. These less smelly foods are suitable if you live in a residential area & don't want to bother the neighbors with the smell. It's good if you're raising the BSF larvae indoors.

If you're okay with the smell & want to go into beast mode, try:

  • Chicken manure/pig manure
  • Decaying chicken, fish, shrimp

The larvae love meat! Make sure these come from good sources so your larvae won't be eating some sickly bits from the start. These more smelly foods are great if you have a bigger raising space that won't bother anyone around. The advantage of these foods is that they boost up the larvae growth pretty fat & fast. From experience, these meat-fed guys are usually very bad-ass. They are stronger & produce more eggs than the ones that are fed with plants mostly.

If you can't find fresh food sources, some people use processed food like:

  • Chicken feed
  • Biscuits/crackers
  • Shrimp feed

Overall, if you throw the food into the ground for 5000 years and it decays, then it's okay for the larvae to eat. If it's in the ground for 1 million year but still doesn't break down (e.g. plastic), then it's a no-no. Hope this brief post was helpful. Good luck getting your black soldier fly colony started.

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