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Random thoughts related to culturing black soldier fly larvae:

bsf closeup on wood

Hermetia illucens-the black soldier fly

Dry Pasta 9/27/9 – I added 1.5 lbs (.685kg) of uncooked pasta to my BioPod last night. Because it was dry and hard I expected that it would take several days for it to be consumed as it gradually absorbed the ambient moisture. When I checked the BioPod this morning all traces of the pasta were gone just 12 hours later.

Sawdust 9/27/9 – I often add a few handfuls of sawdust from non-pressure treated wood to my BioPod. Pressure treated wood contains insecticide, not a good thing for BSF. My feeling is that the sawdust might work as a moisture buffering agent. By that I mean it will soak up excess liquid when it’s present and retain it to help keep the compost consistently moist. Moist but not wet is the perfect balance. The texture of the compost in my BioPod is almost always like potting soil; damp but not sticky and with a loose “fluffy” texture. It’s true that the sawdust adds bulk that will fill up the unit faster, but I don’t see that as a big deal, especially if it results in a more consistently aerobic (aerated) environment.

Shady spot/sunny spot 9/29/9 – Myself and others have stated that a BioPod (or DIY unit) must be kept in full shade, but there are exceptions. The real point is about regulating the temperature of the colony which must not exceed approximately 110ºF internal temperature (BSF reportedly die at 116º). If you live in a hot climate but you’re trying to establish a colony in the spring it might be best to keep your unit in at least partial sunshine. People in cooler climates might find that they can keep a unit in a partly sunny spot all summer. I’ve heard from several sources that black soldier flies are common in Vancouver, B.C., and I expect you could keep a BSF unit in a sunny place there for most of the mating season.

Loose insulation 9/30/9 – The recommended way to insulate a BSF colony for winter operation is some type of rigid material like Styrofoam cut a little smaller than the inside diameter of the BioPod or other unit. The gap at the edges allows the larvae to come up for air and to cool off. To add food scraps you must remove the disc, add the food and then replace the disc.

One time I processed a large quantity of fresh corn kernels. The larvae ate the soft middle part leaving the paper thin skin of each kernel intact. This created a layer of material that floated on top of the waste. It was summer at that time I remember being concerned that the layer would trap in unwanted heat causing juvenile larvae crawl-off into the collection bucket. It occurs to me that in winter you could possibly use some type of insulation that would float on the waste allowing a one step operation when adding new food scraps. I wonder how packing “peanuts” would be? Maybe this wouldn’t provide as much insulation as a solid disc, but in areas with mild winters it might be a viable alternative.

Vacation “feeder” material 10/1/9 – Regular additions of food scraps help keep a black soldier fly colony balanced. Time released food items might be helpful when you can’t add scraps to the unit for several days at a time. BSF seem partial to corn and dry whole corn kernels or cracked corn like that fed to birds might serve as a long term food source for the larvae. As the grain absorbs ambient moisture it will gradually soften so the larvae can eat it. In a relatively dry climate it may be necessary to soak the corn for a period of time. Raw potatoes might also serve this purpose. They contain more moisture so might be preferable in dry areas. I normally don’t condone feeding good fresh food to the larvae, but I make exceptions for the sake of maintaining the colony so it can be used effectively in the future.

The relative rareness of BSF adults 10/1 – I’ve often stated that BSF adults are rarely seen even around BioPods and DIY units full of larvae. Some people have contacted me to say that they aren’t rare on their property because they’ll often see several at a time around their units. I still say that BSF are relatively rare because you might see 4 or 5 at a time, but how many house or blow flies would you attract if you tried? I think the most* BSF adults I’ve seen at once around my unit was 15 and that’s with me doing everything I can think of to attract them!

*I’ve actually seen a few hundred at once, but that consisted of newly emerging adults from my “incubation” bucket that I protect pupae in. I had a few thousand pupae in the bucket and a large number of them emerged at the same time. I don’t count this because they didn’t go to the BioPod, they went into the woods to seek a mate. After mating the males aren’t attracted to any type of food so you probably won’t ever see one of them. The females may or may not return to the BioPod, but if they do it’s still only a handful at a time.

Overfeeding is a common mistake 3/22/10 – People usually run into problems when they first start using black soldier fly larvae to compost food waste. The most common issue relates to anaerobic bacteria which cause foul odors and create a less than optimal environment for the larvae. A very simple way to help moderate these problems is to resist the temptation to overfeed your colony. This is especially true with new colonies made up of only a few thousand individuals. To process waste in substantial quantities you need the equivalent of a 2 – 3 inch layer of BSF larvae. A simple rule of thumb is that, on average, food scraps should be completely consumed within a day or two. Hard items like root vegetables will take longer, and soft items like fruit, dairy products and rotting vegetables may be eaten within hours or even minutes. In cool weather these time frames will increase as the activity of both larvae and bacteria slow down.

The type of food is also a factor. To illustrate this let’s compare processing raw potatoes and watermelon. If you add 10 pounds of raw potato to your unit it may take several days or even a few weeks for the BSF to process them completely (see Vacation “feeder” above). This is because the larvae don’t actually chew food, they scrape away softened pieces instead. This is why they generally target rotting food or manure and are not a pest in gardens. This is also why animal flesh is not their preferred food.* In contrast, if you add 10 pounds of watermelon the BSF will consume it quite rapidly. This will release a large quantity of liquids, and if your unit does not drain well then you are at risk of flooding the compost and encouraging the development of anaerobic bacteria and therefore foul odors.

The skills required to operate a BSF composter are not complicated and the best way to learn is through observation. Watching the larvae work and taking note of the condition of the compost on a regular basis is the best way to get a good feel for how to keep the system balanced.

*It’s fine to add meat products to a BSF unit, but it should be completely consumed within a day. If it isn’t finished quickly then I recommend removing it and discarding it another way.

Starting a new BSF colony using earthworms 3/23/10 – For most people one of the biggest challenges with BSF composting is establishing the colony of larvae. Even in areas with existing BSF populations it can take weeks to attract egg laden females to your unit. A starter kit of BSF larvae is very effective in attracting the locals, but there are other solutions for speeding up the process. BSF larvae are often discovered accidentally in traditional compost piles and also in worm bins. In the past I’ve recommended starting a compost pile to attract BSF and starting an outdoor worm bin would work similarly. However, a person may not want to go through the steps of setting up a dedicated worm bin, so what about simply adding a small quantity of worms to your new BSF unit along with the initial food scraps?

Often while you wait for BSF to discover your new BSF composter you must deal with other entities that find it first, like fungus, mold, bacteria, and a variety insects. The first food scraps you add to the composter can get pretty nasty after a few weeks of waiting for the BSF females. Maybe a small number of worms, and possibly a little soil, would serve to stabilize the waste until the BSF show up. Worms are readily available and I imagine you could find a suitable variety in a nearby bait store for a few dollars. Worms and BSF are known to inhabit the same waste without harm to either species, but if I understand correctly the worms used in this way would probably perish eventually as the temperature rises in summer. Ultimately the worms would serve as food for the BSF. In the case of cooler regions like the Pacific Northwest, the worms might continue to thrive along with the BSF. Combining worms and BSF is an intriguing idea and maybe you folks in the NW have the right conditions to accomplish this.

I haven’t worked with worms so I can only speculate, but if the weather was still fairly cool I believe the worms would survive long enough to

19 thoughts on “BSF random observations

  • May 25, 2010 at 6:36 pm

    Wow, I didn’t know these nasty grubs were useful. I got a nasty surprise one day while emptying out the kitchen scraps into the compost, when I dug a small hole, there were these squirmy things! I was searching the ‘net when I came across this website. I remember seeing a black “wasp” near the compost bin, so the grub things must have been BSF larva.

    Looks like I’ll be keeping the larva in the pile instead of leaving them to the birds as originally planned!

    • May 27, 2010 at 5:54 pm

      Hi Annie,

      “Wow, I didn’t know these nasty grubs were useful.”

      Okay, take it back or I’ll send hordes of squirmy things into your sock drawer. :) Anyway, at least you now know that they’re useful…

  • May 27, 2010 at 10:55 pm

    I have had several “infestations” in my worm farm and did not know what they were or if they were harmful to the worm farm and tried to get rid of them.
    Now I will be grateful when they turn up and may even try to set up a seperate housing for the new guests.

  • May 31, 2010 at 4:25 pm

    Yeah, the BSF larva have shrunk my compost pile, now that I think about it…How long until they become flies?

    • May 31, 2010 at 5:42 pm


      The life cycle of BSF is dependent on temperature. Under ideal conditions (hot) the larvae develop in about four weeks, and then pupate for another two. Keep in mind that the larvae will crawl away from the compost pile when they mature (turn dark) to find a quiet pupation site. You’re not likely to see an adult unless it’s a female that has been attracted to your compost to lay more eggs. They accomplish that in a few minutes and then fly away to die so you won’t see them much even at the pile. If you want to see a female laying then watch the compost on a hot sunny day when there is a good offering of kitchen scraps; that’s the most likely time you’ll spot a few. Good luck!

  • May 31, 2010 at 10:28 pm

    I am so glad I found this site!!! So much information!!

    I live on the second floor of an apartment and I was trying to compost my kitchen scraps (first timer here) so I had no idea if I was even doing it right.

    I’m using an old tote bin i had lying around….anyways I had way more wet scraps than dry browns as the saying goes and the bin starting smelling awful (like a putrid dumpster) and lots of insects- one of which were these black “wasps” which i was terrified of being stung by!

    So I left the bin alone and covered it with dirt to smother the smell and noticed these eggs all over it which i thought “oh great, now i’m going to have maggots and house flies all over the place!”

    well long story short, i went to turn the pile tonight because i am not one to give up so easily and i almost jumped off my balcony when i saw these HUGE maggots!!! I knew they werent maggots but grubs of some kind because they were HUGE HUGE HUGE!!!!

    i did a search and found your site which now has me convinced to keep my little pet composting project instead of throwing it in the dumpster!

    I do have some questions though, what happens if the grubs cant find their way out of the bin? will they die in the bin? will they be able to climb out vertically? (i’m sure my downstairs neighbor won’t be to happy to find grubs falling from my balcony, haha!)

    i’ll have to configure some type of contraption i guess so they can crawl out and i can let them reach adult hood.

    i just hope they are black soldier flies and not something similar and i am mistaken!!!

    thanks again for all the info on your site!

    • May 31, 2010 at 10:58 pm

      Hi Karina, I’m glad you found my site too! :)

      I’ll guess that you do have BSF larvae because of the size and also your description of the “wasps”. To be accurate BSF larvae are indeed a type of maggot, but as you now know that’s not a bad thing. The term “maggot” is just another word for the larvae of any of the over 100,000 species of flies. I don’t normally use the word maggot because of the prejudice almost all of us have towards any type of fly, even the harmless and beneficial black soldier fly. It’s kind of like the situation with snakes; there are a handful of dangerous species and the result is that most people are hateful towards all snakes.

      The larvae can crawl up a smooth surface if there is condensation present. If you keep a lid on the unit it will encourage condensation and unless it’s extremely snug fitting the larvae will squeeze out when they’re ready to leave. Setting up a ramp system will take the guess work out but if you’re going to start modifying the bin you might consider building a BSF-specific unit like my bucket composter. I’ve been processing up to a pound of waste per day in the one I’m currently testing. Of course you could operate both your present bin and an additional BSF unit too. The bin your using now isn’t a very good place for the larvae to pupate, but they will do it if they aren’t able to crawl out. In that case you’ll find adult BSF inside occasionally.

      If you want to be sure you have BSF I can probably tell from a close up photo if you can upload one.

  • May 31, 2010 at 11:25 pm

    Thanks for the quick reply!!!

    And I had no idea about the “maggot” part, very interesting and makes sense. I always enjoy learning new things!

    The lid i have on there is one that has two sides that fold onto each other – kinda like how you close an open cereal box at the top by folding one flap into the other. Also there is a ton of condensation that builds up and the flaps are not tight – thats how they got in there in the first place i suspect.

    From what you say they will be able to crawl out due to the condensation and the loose fitting lid.

    Should I just let them do so on their own? I don’t have any money whatsoever to build that nifty bucket as i’m not working and going to school right now, but maybe i can scrape up some parts lying around or just wait until i have the funds. I do have some buckets but no lids and no piping :(

    This is all new to me and very interesting and exciting as i love science and experimenting!!!!

    Unfortunately i will have to wait until tomorrow to try to get a pic, it’s nightime and my cam phone doesn’t have a very strong light.

    Thanks so much for your answers!

    • June 1, 2010 at 7:19 am


      Most likely the larvae in your bin came from eggs laid on the outside of it. Unlike houseflies, BSF females don’t lay their eggs directly on waste which is part of the reason they are not vectors of human pathogens. Typically the females will deposit eggs randomly on the outside of the bin or in a cluster in some crevice that is part of the bin’s design. Then when the tiny larvae hatch they are able to crawl into the bin through any small opening larger than a pinhole.

      It sounds like the larvae won’t have a problem exiting your bin the way it is. If conditions change and you stop getting condensation you have a few options. You can tilt the container so that one side is at a 45º angle which will allow the larvae to scale it even when dry. In that case you might need to leave the top open because when it’s dry the larvae won’t be able to scale even a very short distance vertically. You can also mist the sides of the bin with water in the evenings. If for some reason you want to capture the larvae as they escape you can set the bin on a larger tray or inside a larger bin with a shallow layer of sawdust in it. As the larvae drop from the lip of the compost bin they then land in the sawdust and because it will be dry they will be contained by any vertical surface taller than an inch or two. To separate the larvae from the sawdust you can pass it through a strainer that is just open enough to let the sawdust pass through.

      The option of just letting it be is also a valid approach. I believe most of the larvae will find a way out when the time comes and those that don’t will probably survive and pupate in the bin.

  • June 1, 2010 at 9:53 am

    Thanks Jerry!

    I did notice the random eggs on the top of the lid. Also the lack of other flying insects, only one house fly and about 2-3 fruit flies.

    Unable to get a pic but upon much closer inspection of the wigglers, they look exactly like the ones you have in your photos and video. I’ll let them be as they look happy and content in my bin. I did add some more shredded paper as it was sopping wet in the bin.

    I’m going to start giving them my kitchen scraps again! I just felt like a failure for not being able to compost but not anymore!!! AND it is good to know I am able to give them meat as I felt terrible not being able to compost meat scraps. What a blessing in disguise.

    Thank you for all the good info and you are so nice!!! I wish more pages on the net were as informative as yours.

    • June 1, 2010 at 10:29 am

      Thank you Karina!

      You will need to watch out for excessive wetness in the bin, especially if you add kitchen scraps regularly because they typically contain a lot of moisture. Standing liquids in the bin will probably lead to anaerobic conditions and the related foul odors. I would also be careful about adding too much meat. As a general rule if it takes more than a day or two for the larvae to eat something you’re probably overfeeding them. This can also lead to anaerobic conditions and with meat products it’s important to avoid that. Naturally hard items like raw potatoes, etc., will take longer to break down, but softer stuff should disappear quickly.

  • June 1, 2010 at 11:34 am

    Thank you Jerry :)

    I’m leaving the lid open today to help dry it out a bit (and hopefully attract some more BSF’s!!!) and I have several holes on the bottom and sides to help drain. I will keep that in mind about the meat scraps too.

    Wow I am excited! Haha!

  • July 5, 2010 at 12:00 am

    i have a question about how you pupate your grubs when they are ready to pupate? I read “incubation bucket” bucket,if i may ask how do you have that set up,i just recently started my colony and have a few adult grubs crawling out of my bucket that i have them in.
    thank you.

  • July 6, 2010 at 4:31 pm

    A little background and a few more questions (I am totally new to this!):

    I actually stopped putting anything in the composter, and I transferred anything that the grubs seemed interested in a few days ago.

    I have a worm bin in the garage, which is where I initally found the larvae. Of course, I thought I had maggots! That is how I found out about the BSF (I was looking for the fastest, non-toxic to my worms, way to get rid of the “maggots” fast!). Since reading about them about a month ago, I have been obsessed! I needed to sort through the vermicomposter anyway, so I did that and sorted out the BSF larvae. Because of the increase in humidity in the worm bin (almost soggy), I began easing off high water content veggies and turned in shredded paper and high cellulose plant material. So…no BSF there as of now – although my worm population more than doubled in the few weeks that I saw the BSF. It seems that, outside of the moisture issue, they love each other! Within days of not seeing them in the vermicomposter, they showed up on the other side of the house (outside) in the tumble composter. I made your bin and began collecting larvae, as well as trying not to add to the tumble composter. However, if I put the bucket anywhere outside (even elevated), ants are seeming to find a way in. I don’t want to spray too much in the backyard because my daughter and dogs like to play out there. We are in the middle of a massive mosquito outbreak, so I am worried about putting it in water. I figured that the BSF found the worms in the garage first and seemed to be happy there, so I put it right next to the worm bin with cardboard sticking all over the worm composter (that now looks like it has a spiky hairdo from all the cardboard rolls I adorned it with)! Nothing! I have taken to putting the bucket by the composter for short amounts of time in the afternoon when I see more of the flies buzzing. This may sound crazy, but my bucket is bright orange-do you think that has anything to do with it? I can’t fit the cardboard pieces into the composter grooves because they are curved on all sides and very small/shallow-it just falls out.

    I do have a few questions about the bucket construction:

    My grubs had NO problem going into the filter media. They were so entangled that it seemed like they were just crawling in, getting trapped, and dying. I finally cut it apart and freed them one by one! It was horrible. As of now, there is nothing on the bottom and a golf ball is blocking the hole to the drain hose. Was this normal for them to do? Also, I have trimmed, turned, and twisted my little milk jug ramp. I cannot get the thing to lay flat against the bucket. Does a small gap matter or will they get stuck in the space behind the “funnel”? Lastly, I have a cross cut paper shredder. Do you think that I could use that vs. sawdust in the collection container. I put a few in there, and they buried themselves. I haven’t seen much of them since!

    Thank you so much for your time! I appreciate any suggestions or insight you might have.

  • July 6, 2010 at 8:38 pm


    Just to set the record straight; “maggot” is just the common word for any fly larva, so BSF larvae are maggots also. Unfortunately the term has taken on a negative meaning and most people don’t understand that not all of the 100,000+ species of flies are harmful pests. I use the term maggot everyday when I discuss my hobby with my girlfriend, family, or neighbors, but I stick to the more technical term “larva” or “larvae” on the internet because I don’t want to prejudice people who are just discovering BSF. In the end words don’t matter, what matters is that the larvae of the black soldier fly are harmless, beneficial, and fascinating creatures.

    I think the problem with ants will be less of an issue once you get a colony of larvae established. I’ve never had a serious problem with ants and I hear the same from others who have established systems. I do remember spraying insecticide on the legs of a stand I was using for a BSF unit, but I haven’t done that in a couple of years. Recently someone commented about using oil as an ant barrier instead of water. It seems like it might be effective.

    I don’t think the color of the bucket is a factor. You’ll be fine if you just keep adding larvae and eggs manually, and keep the “good” waste in the bucket. One thing to consider is that BSF may be laying in the bucket and you don’t realize it. Often the females simply scatter eggs randomly on the inside wall, and these are virtually invisible. Then, once eggs are laid, it takes four days before they hatch. The newly hatched larvae are so tiny that it’s almost impossible to see them in a waste pile for several days until they’ve grown to several times their original size. In short, it takes longer than you probably expect to see noticeable results. Keep doing what you’re doing and it will happen soon enough.

    The filter and drain system is a work in progress. Whatever filter is used, the larvae will crawl through it. You might want to question whether or not the larvae you observed were actually trapped or dead. The larvae are pretty good at wriggling through tight places and just because they’re motionless when you look at them doesn’t necessarily mean they’re dead. All creatures rest, and BSF larvae also go through several transformations as they develop. I think that often when we see a motionless larvae we’re looking at one that is preparing to shed its skin and pass into the next stage. The filter might just be an ideal place for them to wait while this happens. Finally, some larvae may die as a result of this process. The fact is that nature designed BSF larvae to have a high mortality rate. A single pair of BSF produces 500-900 eggs, and if they all survived then the BSF population would get out of control. Instead only two larvae must survive to successfully reproduce if the population is to stay stable. I don’t see a problem with increasing the BSF population, my point is that we’re bound to extend the life of some larvae and shorten that of others. It’s just part of the process. Having said that, you can certainly experiment with different filter materials. I still haven’t found the perfect one yet. If you look at the most recent version of the bucket composter (2.1) you’ll see that I cover the drain outlet with a halved golf ball.

    Are you holding the funnel in place with magnets? The soft plastic of the water jug should be held tighly against the bucket wall if you use strong magnets. Some larvae may squeeze behind the funnel in places, but that shouldn’t be a problem. If you place the magnets by the edge of the funnel it will stay tight against the bucket the larvae will crawl around them and into the tube. Keep in mind that this diy unit does require regular adjustments to maintain a high level of functionality. Hopefully as I get feedback from people like yourself we can find ways to make it even better.

  • July 9, 2010 at 7:18 pm

    so i’m new to bsf’s i just wanted to know if all soldier fly’s have the same nutrients and if my bucket would attract other species,i am just asking because this yellow bsf was in my house looked just like a honey bee “stratiomys potamida”

    • July 9, 2010 at 9:07 pm

      Hi akuma,

      In response to your first post I’ll paste a portion from the starter kit page:

      The dark mature grubs will gradually accumulate in the collection bucket. In an established colony you could feed these grubs to pets, livestock or wildlife, but when starting a new colony they should be allowed to pupate into adult form (winged stage) and mate. A typical BSF unit is not a closed system which means that the adult BSF are released so they can mate outdoors and then return to the unit to lay their eggs.

      A BSF unit at full capacity will have enough larvae in it to cover the surface area with few inches of solid larvae, maybe more. Until you achieve that density you should focus on building up the colony. I don’t recommend feeding any mature grubs to animals until you completely establish the colony. Each pair of BSF that you sacrifice as animal feed represents 500-900 eggs that might have been laid in your unit. I also don’t recommend scattering the mature grubs on the ground while building up a colony. I think it’s best to protect every mature grub until your colony is at capacity.

      If you scatter the collected mature grubs on the ground that leaves them vulnerable to the many predators that target insects. It’s fair to assume that only a small percentage of released grubs will survive to become adults. It’s best to keep the mature grubs in a container such as a bucket with a lid to protect them. The container needs to have several holes with a diameter of at least 3/4 inch to allow the emerging adults a way to escape. The holes will also provide necessary air for the pupating BSF and also aid in keeping the temperature regulated. Like the BSF unit, this prepupae container must be completely shaded and protected from rain. Adding an inch of bedding material such as sawdust (not pressure treated), peat, etc to the container will encourage the grubs to pupate, but it must stay dry and loose so the emerging adults can climb to the surface.

      For your last question; I imagine the nutritional value of BSF larvae would vary depending on diet and other conditions, but I have no specific knowledge about that. Your bucket composter will noticeably attract other species in the beginning, but once you have a dense colony of BSF established then there will be very few other species.

  • August 17, 2011 at 5:32 pm

    Hi there, I’ve been conducting a series of tests to see whether or not the liquid waste produced by phoenix worms (BSFL) can also be used as a mean of attracting adults.

    Thus far I have only tried in Louisiana and Mississippi. I have found it easier to sustain my population in Louisiana, but I did notice that regardless of location having a small amount of odor did increase colonization slightly.

    Keep in mind my sole intent was to calculate colonization probability models, so every time I would have to bleach containers and find new locations with similar (or as close to as many simulations as I could control given my budget) conditions. I found that it did, over a four month interval, increase the probability around seven percent. My problem being that due to financial limitations I was only able to establish six colonies at a time (3 in each location). Once I saw the presence of the population, I would cleanse the locale and move along. So, I was only able to obtain a very small sample (20).

  • July 8, 2012 at 10:30 pm

    I have just started using a rolling composter with a tight fitting lid. Thank goodness for the NET, because I thought I had a problem when I noticed all the grubs in the compost bin. My question is, I guess the grubs will die at some point, because they will be in the bin forever, and won’t be able to get out as flies? There are air holes of course, but they are pretty small. I don’t think the flies could get out of the bin. I’m guessing there were some eggs on some of the brown matter I tossed in. Is leaving the grubs in there to die ok? I take it that they simply add to the quality of the compost? I’m composting for good nutritious dirt for the garden, not for grubs to feed to chickens. Thank you.

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