Here are some low-cost feedstock ideas for the black soldier fly larvae and some pros and cons.
#1. Coffee grounds
The smell of coffee grounds accidentally attracts natural BSF in the area. So while feeding your larvae with this foodstuff, you may get a double benefit of attracting more BSF to the bin. As coffee grounds are steamed and heated, they are comparatively more sterile than the other feedstocks. The moisture of the grounds is also nice for the grubs.
The downside to this, however, is that not everyone is a coffee drinker. If there's a coffee shop near your local area and they are having the grounds as waste, then it may be a good idea to ask for some from them.
#2. Seasonal fruits/veggies
In some places, growers feed the BSF with seasonal fruits and veggies. Or basically whatever is available in an abundance for cheap. This could be cheap watermelons, left-over dragon fruits, papayas, pumpkins, sweet potatoes, the coffee berries, etc.
The plus side of this feedstock is that they don't smell too bad like some meaty stuff does. Also, they can be had for very cheap, which helps lower your feeding costs.
On the other side, not all fruits will be eaten by the larvae. For example, they don't really enjoy the skin of citrus fruits. Because of the minty terpene oil in it. They do eat the flesh of citrus however. No avocado seeds or rinds will ever get eaten. But the flesh of the avocado is fine.
Another thing to look out for is the potentially harmful pesticide or chemical residues in some fruits and veggies. Some fruits like watermelon can be quite watery.
#3. Animal manure
The animal manure that work out well for BSF larvae are chicken manure and pig manure. These are carnivorous animals that feed on more high-protein stuff. Chicken manure, however, may heat up the growing area quite a bit. If you find this to be an issue, try rabbit poop. This stuff doesn't heat up the bin and has a nice moisture to it which the grubs like.
Cat litter is also okay for these little guys. It may be quite dry however. So before feeding, you could use a spray bottle to moisten it up.
Manure from grass-fed animals like cows, goats or horses may not be the best for the BSF. Because they are quite fibrous and contain the lignin or cellulose, they may not get digested well in the BSF intestines. The bio-conversion rate for the herbivore manure is around 6-10%. You may get 20% bio-conversion with higher-calorie feedstocks. And the obvious downside of using animal manure is the smell.
But again, the cost is cheap and the supply is abundant. The larvae grow quite strongly on these high-protein, high-calorie stuff compared to the fruity ones.
#4. Left-over foods
Oily, cooked foods are also fine for the BSF grubs. They tend to chew on down softer bones like fish or chicken bones faster than mammalian bones. If you have some stale, expired oatmeal or chips, those will work as well. Remember to moisten them up before feeding to make it easier for the grubs to eat and convert.
Anything that's too woody or stemy like broccoli stems may be better for the worms, not these guys. They do eat banana peels however.
#5. Other feed ideas
- Soybean waste
- Pond mud
Responses to Readers' Questions
My BSF larvae are dying while feeding on pig manure. What could be the issue?
--> Thanks for your question. In a reply via email, here are some notes again for consideration:
To start with the pig manure issue, in the feeding area you could check if there are darkened prepupae and cream larvae both developing. When the dark prepupae are about to crawl off, they will excrete out all the contents in their guts. This dark poop, from some growers' experience, if not collected, may affect the growing cream larvae. When the cream larvae meet this stuff, they may have a less appetite to eat or vomit out the food they've consumed. This could gradually make them shrink smaller in size and die off, and turn the feeding area quite mucky. If you notice this may be the case, you could filter out the dark prepupae poop in the corners where they gather. Some growers harvest the black ones out when the box is about half darkened. From an observation, early harvest when there are a few dark prepupae may cause the cream larvae to quit eating and follow. This could lead to premature crawl-offs.
Around your growing area, check if there's any scent of insect sprays, chemical sprays. The larvae are sensitive to these and some contact may turn them motionless. If it is not long after your larvae stop wiggling actively, you could try sprinkling a thin layer of yummy food (like chicken feed) to stimulate them to wake up again. They may wake up again but wiggle quite weakly at first. Some believe such food poisoning may turn the larvae inactive, but good news is they may not be dead yet. In a similar case, a grower was able to re-activate the larvae from chicken mite sprayers in chicken manure with that simple tip (https://www.youtube.com/watch?v=1_10vw4s0NE).
Lastly, for a whole picture, you could check other aspects like temperature (make sure it's not too heated up especially in the center of the box), oxygen, and just enough feed for the BSF so fungi or other bacteria won't grow on the pig manure.
I'm not sure if these pinpoint the problems and answer your questions. But I hope this helps.
I recently discovered that my bsf pupa disappeared after living them in a crate overnight. Do we have predators feeding on the pupa?
--> Thanks for your question. Have you checked inside underneath the sawdust? The prepupae may bury themselves underneath to undergo metamorphism into flies. They need some darkness at this stage. When it's time and they are ready, they will automatically crawl up to the surface.
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