This method doesn’t involve the dark, prepupal larvae which are self-harvesting

The coffee colored black soldier fly grubs (prepupae) are the final stage before pupation into adult BSF (Hermetia illucens). To our advantage they are programmed by nature to crawl away from the food source in search of a suitable pupation site. In a properly designed BSF unit these larvae crawl up a ramp and drop into a collection bucket where they will live for weeks without any maintenance.

The method described below is for harvesting the earlier stages when the larvae are actively feeding and growing. It doesn’t work for the mature larvae because they don’t eat therefore aren’t attracted to the bait in the collection container. It works very well for the light colored immature larvae.

The Immature Larvae Collection Device or ILCD (old butter tub)

Take a cheap container and cut some small holes around the bottom edge.

immature larvae collector with fish pellets

(click on images to enlarge)

Add something delicious (any food scraps will do), and simply place it on the surface of the compost. I used moistened fish food because I’m training my fish to eat it and this is a good way to introduce them to the flavor (I feed the larvae to the fish). Just about anything will work, but fresher items will make handling the collected larvae more pleasant.

The photo below was taken 2 minutes after placing the tub on top of the compost.

immature larvae collector after 2 min

This is after 11 minutes.

immature larvae collector after 11 min

The photo below was taken 40 minutes after adding the container.

immature larvae collector after 40 min

This quick harvest totaled about 2 cups (.5 litre) of small to medium larvae. I don’t have many large larvae at this time due to the crash I caused in the colony a few weeks back. I do have a lot of larvae, just not large ones yet.

fishing, bait,

Tagged on:     

30 thoughts on “Collecting the immature larvae

  • July 27, 2008 at 1:16 pm

    Wow, that’s great!!! You could use this to test which foods they like best by timing how long / how may come to the food.

    Question: Why did they stay in the container and not leave as soon as the food was gone? Looks pretty crowded in there like they couldn’t get out (which would be good if actually trying to catch them).

  • July 27, 2008 at 1:22 pm

    Follow up on my question: I’m wondering if you could simply dig a little hole into the compost and take a container (say a large empty container of yogurt) and place it so the top/rim is at the level of the compost. Put in some food and let the larvae crawl in but they can’t crawl out? Would that work for catching the younger ones?

    I’m also wondering if you could add small holes, say 1/6 inch, that would allow the really small ones out, but keep the bigger ones in?

  • July 27, 2008 at 1:31 pm

    Hey Nifty!

    The larvae come into the collector like the tide rises and lowers. Once they’re all in there it takes a while to find the exits. :)

    I think the yogurt container would work but I don’t know if it would be worth the extra steps. I literally just put some food in the tub and set in on the compost. 5 seconds total.

    I haven’t tried to sort the larvae for size yet. One thing to watch for is that large larvae will try to wiggle into an opening that’s too small and get stuck. (I said they were fascinating, not bright :) )

  • July 27, 2008 at 1:34 pm

    I’ll experiment!

    Jerry, I don’t have any fish meal around. What is your top 10 list of food stuffs to tempt these guys? I think dog food is atop your list, but I don’t have this either.

  • July 27, 2008 at 1:56 pm

    I’m trying to think of something they WON’T flock to! At this very moment I’m testing plain steamed broccoli and french toast with maple syrup. So far the french toast is winning. :)

    I plan on running a series of tests to see what they’re preferences might be, but I think this method would work fairly well with most foods.

    The main reason I used fish pellets in this case is because I’m using the larvae to feed train my fish. The fish love to eat the larvae so I feed the larvae some fish pellets and also coat them with a mash made from it. That way the fish get a taste of the fish food every time they eat a larvae. I’m not sure if it will work but it seems reasonable.

  • July 27, 2008 at 3:43 pm

    Jerry, I put out two containers, one with 1/2 side rice and 1/2 side mac-n-cheese. The other one has damp “wet cob” that is for sheep and has mashed corn, oats, and molasses?

    If I turn the soil I see a TON of BSFL but none are venturing into the container. My bin allows a tiny bit of light inside, is that the problem (they won’t venture to the surface). Does your container keep all light out? Maybe the holes in the bottom allow them to go into the container from under the ground? Maybe they just don’t like the food I’m providing.

    Looking forward to your list of best baits for BSFL!

  • July 27, 2008 at 4:18 pm

    One thing to keep in mind is that the larvae in my unit are all in a mass within 2-3 inches of the surface. Turing the compost in your traditional unit disperses the food, and therefore the larvae, throughout the unit. That’s not the case in a device specifically designed for BSFL. Even so, I think the only real difference would be that it will take longer to attract the larvae in your compost bin to the collection cup.

    My active colony is still in my old homemade unit because I’m starting my BioPod from scratch. My old box lets in quite a bit of light compared to a BioPod and I can’t be sure what kind of difference that might make. Even with the top off I can entice the larvae to the surface with new food.

    BSFL like almost all food. :)

  • June 14, 2009 at 7:11 am

    Hi Jerry,

    Thanks for your immediate response to my inquiry earlier. I appreciate it. Another inquiry here: Would the feed compost for the BSF larvae be very wet as in the case for ANC worms? I saw your fish meal bait and they were very dry. Where will they get the necessary moisture/water? Thanks in advance.

  • June 14, 2009 at 8:10 am

    armand, you can’t tell from the photo but the fish pellets were moistened. The BSF may still have been attracted to dry pellets, but the water increases the smell which I believe is how they find new food. When it comes to eating the pellets you are correct that grubs are more efficient at processing food that is fairly moist. I edited this post a little to make it more clear, thank you.

  • July 23, 2009 at 12:19 pm

    I’ve been trying various techniques (short of buying a Biopod) this summer. When I handpicked a bunch of BSF grubs from the compost pile and put them in a container, they did a fair job of self harvesting, so long as there was minimal food in the container. Otherwise, they seemed happy to pupate in situ.

    Have been trying your technique too. It did take the grubs awhile to find the plastic container with wet fish food on top of the compost pile but they eventually showed up, mostly just below the container but some made it in. I kept making the holes bigger and bigger because the grubs would clot the holes and so would the gnarly stuff they rendered out of wet fish food. (It stinks pretty bad.)

    I put black plastic over the pile to minimize light but the birds kept tearing that away, so then I put a light piece of plywood. They are definitely in the vicinity but your concept is not working as a self-harvesting technique.

    I’m willing to experiment if you have further ideas.


  • July 24, 2009 at 8:44 am

    Hi Rebecca,

    Maybe you don’t have a sufficient concentration of BSF for this technique to work well. Also, the colony needs to be a little hungry because if they have ample food available there is no motivation for them to seek the food in the container.

    I don’t understand how any food as desirable as that would become anaerobic (stinky) in a healthy BSF colony. In fact, bad odors are a dependable sign that your colony is out of balance. Did you leave the baited container in place for a long time? The whole process is over within an hour or so when I’ve done it. I suspect that the bait was not eaten completely and that it sat around for a long time without the attention of the BSF. If the grubs had completely eaten the food it would have been reduced in volume by 90% or more. As far as their residue being stinky, I’ve got about 40 pounds of it in my BioPod currently and you can stick your head right in there without noticing any foul odor.

    I also wonder about the grubs clotting the holes. My newer version has half inch diameter holes but in my first one they were smaller and the BSF would still flow in fairly quickly. If the holes are big enough for a single grub to pass then it should work, just maybe a little more slowly.

    When you tried the collection technique was it in your BSF container or on the traditional compost pile? I’ve only used it in my BioPod but it should work equally well in a decent DIY unit.

    If you send me a photo of your unit/colony I might be able to give you better advice.

    Concerning BSF pupating inside your DIY unit; if they can’t get out then eventually the grubs will have no choice but to pupate by the food source, but their instinct is to migrate away to a dry, quiet spot. One thing you can do to help them climb out would be to tip the container until the wall is at a 40-45 degree angle. You could so this for a few hours every 2-3 days and the mature grubs will probably crawl out. You may also see some juvenile grubs crawling out depending on several factors like temperature, colony density, available food, etc.

    Here are some photos from my updated collection unit. The grubs in the photos below are part of an eight pound harvest. The series below was taken over a one hour period and I repeated this process a total of three times to get that amount.

    Juvenile BSF grub collector Juvenile BSF grub collector-baited 4.47pm Juvenile BSF grub collector 4.55pm Juvenile BSF grub collector 5.21pm Juvenile BSF grub collector 5.43pm

    (click images to enlarge)

    Thanks for sharing your experience Rebecca, please keep us posted.

  • July 25, 2009 at 9:37 am

    I do not have a biopod but I do have BSF grubs. They showed up in a compost pile and I have tried various experiments by hand harvesting them and moving to different containers, and by using the compost pile as a container.

    Now, the compost pile is pretty composed, so I hollowed out an area on top and set the container there and covered it. After a couple of days, they migrated to the food but were never able to access it well.

    Per your latest comments, I drilled 1/2″ holes around the perimeter of the bottom and that sped things up quite a bit. I also put in less of the moistened fish food. What you demonstrate about in a matter of minutes, also occurred for me, in smaller numbers, over a matter of hours.

    At some tipping point, when most but not all of the food was converted into a mealy matter, which I presume is waste and which did smell bad, the grubs went into a sudden exodus mode.

    So things are looking better. I’m trying another round today. The current issue I’m addressing is when to harvest? If I do it at grub peak population, there is still quite a bit of food intermixed. If I wait, there are considerably fewer grubs.

    I see you started with mashed food. Do you think that makes a difference?


  • July 25, 2009 at 2:29 pm

    Hi Rebecca,

    You can keep a BSF colony in any container or no container such as your compost pile. Managing a colony will be different depending on the container. A BioPod adds convenience and efficiency to BSF culturing by making it relatively easy to regulate moisture and heat, contain the grubs, protect the colony from predation, and to harvest the mature grubs.

    BSF grubs in all stages are highly mobile and they will migrate away from a food source for a few different and commonly occurring reasons. If it gets just a little too hot in the colony the grubs will try to crawl away. In an open situation like a compost pile it’s not likely that many of them would return. If the amount of ready-to-consume food is insufficient to support the number of grubs in a particular food source I believe a percentage of grubs will abandon that food source and migrate away. A well designed BSF unit will effectively contain these migratory grubs. A BioPod or good DIY unit will provide us with a “captive audience” of concentrated and hungry BSF allowing us to maintain a colony that is more densely populated than a naturally occurring one. It’s this condition that gives us the ability to process so much food waste so quickly and efficiently.

    BSF grubs naturally avoid light (photo-phobic). You’re likely to have better luck with your collection tub if it has a lid that blocks light. The series of photos I posted above was taken with the BioPod cover off, but it was replaced after each photo. I’ll mention this in my related posts if I neglected to originally.

    The waste in a BSF can be stinky for a couple of reasons. If it was stinky when you added it then the grubs won’t make it any less stinky, at least not for some time. A balanced BSF colony smells like whatever you add to it, plus a smell that could be described as wet straw. Typically if you have foul odors in a BSF unit it’s because you have anaerobic conditions. Anaerobic bacteria are those that thrive in the absence of oxygen and the usualy result is a sewer type odor. Normally BSF grubs will effectively churn waste as they consume it and in doing so they carry air throughout the pile and maintain aerobic (with oxygen) conditions. Under those circumstances you will not experience bad odors. Anaerobic conditions can result from an accumulation of liquid which prevents air from getting to the bottom of the unit. It could also happen from over-feeding a colony because they don’t have the capacity to effectively churn the waste. In your case it sounds like the fish food paste sat around uneaten in a warm environment. As I said before, if the BSF had fully consumed the fish food it would have been nearly gone.

    The food I used for bait in the series above was a mixture of cornmeal, fish pellets and water. I use a paste because the BSF can’t eat dry food and it also stays in the container better. You could use a wide variety of food for bait, especially if the grubs are very hungry. As I stated above, you aren’t likely to find very hungry grubs in an open compost pile because they migrate out the moment they perceive a lack of food.

    I look forward to hearing about your progress! Thanks.

  • July 26, 2009 at 3:06 pm

    Great info, Jerry. Thanks. You’re a real pro at this.

    I have a piece of plywood over the top of the compost pile and a population is staying in the area. With larger holes and smaller amounts of food to start, I’m able to harvest modest amounts–appetizer quantities for the catfish.

    Today I started a new compost pile. Removed the plastic container and shoveled a bunch of the BSF grubs swarming underneath to the new pile, right on top of kitchen scraps.

    Could you send a link for what you consider to be the best DIY harvesting system? Any advice on how to deploy cardboard in the vicinity of the compost pile to optimize egg laying?

    Thanks again,

  • July 27, 2009 at 9:43 pm

    Rebecca, I’ve been trying to get a minute to respond to your comment but it’ll have to wait until tomorrow. I’ve just about finished a very simple DIY BSF composter and I hope to post it in a day or two.

  • July 30, 2009 at 10:37 am

    I look forward to hearing about it soon.


  • August 1, 2009 at 3:55 pm

    Hey Jerry,

    I love the website, it has lots of very pratical and useful info. I am doing research on breeding BSF larva for my reptiles and then expanding operations to supply fellow collectors, my question is this, with your setup being outside how do you keep it clean of parasites…….specifically mites?

    My setup will be most likely indoors so that leads me to a second question…..breeding, is it viable to take say 20 pupae and place them in a 2 gallon jug with a lid and let form into adults which would then breed and lay eggs all within the same jug?

    Thank you in advance for any advice to accelerate my learning curve.


  • August 1, 2009 at 5:23 pm

    Hi Jason and thanks.

    I have to be honest and say that I haven’t considered mites. I only feed my grubs to my pond fish and I’m not aware of the problem. I do know that when Dr. Sheppard raises BSF larvae for sale as Phoenix Worms (his brand) he does it under controlled conditions to eliminate the concerns of pet owners who buy them.

    Maybe you could tell me something about mites. How would they enter the system? Would they cause problems if the BSF grubs were consumed immediately by your pets?

    I’ve wondered if a bath in a mild bleach solution would deal with the parasite issue. Maybe you could even feed a grain paste to the BSF that contained a very small percentage of bleach. Humans treat water this way and I’m pretty sure BSF could tolerate it. Perhaps you could let the breeding happen outside where it’s simple to manage and then bring the juvenile grubs inside for a “cleansing diet”. Once indoors and purged the grubs could be fed a sterile grain mixture until it was time to feed them to the pets. I’m pretty sure there’s a way to deal with this issue given an outdoor breeding population.

    Indoor breeding can be very tricky from what I’ve heard. I’ve read that BSF need at least a few square meters of space for mating since it’s usually done in flight. I know indoor breeding has been done, but I have no experience with it.

  • August 20, 2009 at 11:46 am

    I followed one of the suggestions about putting food scraps on a paper plate & just setting it in the bin on top of the compost. Ants crawled all over it. The food stuff is mostly asparagas stems.

    What do the ants mean & are they hurting the grubs/compost. I am not sure if they are fire ants or something else.

    How do I get the ants out of the bin?
    Thanks for any help offered.


  • August 20, 2009 at 12:04 pm

    Salli, having BSF in a traditional compost pile if great, but you really can’t control what happens with that type of arrangement. A dedicated BSF unit would typically be on some type of stand and you would treat the legs to repel ants. For my DIY bucket bio-composter I deal with ants by keeping it in a pan of water creating a moat they won’t cross.

    Some types of ants might not bother the BSF other than competing for food, but I know that some will prey on the eggs and maybe on the grubs too.

  • September 13, 2009 at 3:14 pm

    Jerry, What BSF stages are safe to feed to chickens and/or ducks. Also, should I limit the amount of BSF grubs I feed to my poultry or can I feed them too many and make them sick?

    • September 13, 2009 at 3:50 pm

      Hi SuunyD! (or is it SunnyD?),

      All stages of the larvae are safe to feed to animals. If you tried really really hard you might be able to produce some toxic BSF larvae but you would have to consistently feed the colony with putrid meats, etc. If your colony smells like death you’ve done something terribly wrong and I wouldn’t feed the resulting larvae to another animal. BSF are repelled by the anaerobic conditions that lead to that type of toxicity so it would be difficult to mess up so badly.

      I don’t know anything about chickens except that their meat stays moister while cooking if you brine it first. :) If they’re anything like the stray peacock (hen) that showed up at our place I might have a clue. I’ve trained the peahen to come and take BSF grubs from me and often I’ll give her all I have with me. (She comes around when I’m fishing at my pond.) A few times I had several hundred larvae and in those cases she reached a limit to what she wanted and stopped eating on her own. She’s a big bird of course and she’s eaten a few hundred at a time I would guess.

      If you want better info about chickens you might try posting in this thread at Backyard Chickens:

  • August 26, 2010 at 1:33 am

    Hi Jerry, thanks for your reply regarding my biopod not functioning properly. I took your advice and read all the info available on your “tips & tricks” section. Now I understand that my problem was one of the coir filter becoming clogged, and also perhaps in my overfeeding the larvae. while I still do not understand how the biopod surface should look when it contains just the right amount of food for the larvae, I now know that I must very soon empty out the biopod and begin again, this late in the season. It stinks like sewage, and has been for at least a month. It will take a bit of shopping to come up with a new filter system, but hopefully I will get that together very soon. Thanks for all of the advice that I never bothered to access earlier this summer when the putrid smell began (I thought that was normal). I had also had a set-back when we went on a long weekend vacation and the fluid collection jar on the bottom of the biopod filled and backed up liquid into the biopod. I took it off and simply placed an open container underneath the biopod, which is a LOT easier to empty.

    • August 26, 2010 at 7:01 am


      You’re very welcome! I never had a drainage problem after installing the layer of coir in my original BioPod. The main difficulty with coir or any other filter material is that the larvae will tend to expand it to the point where it becomes ineffective. If you look at my DIY bucket composter you’ll see how I’m dealing with that presently. Soon after getting my original BioPod I decided to replace the liquid jar with a straight drain. It’s worked very well for me and you can find details on how to do it on the “tips and tweaks” page.

      Good luck and please let me know if you need help.

  • September 15, 2011 at 10:09 am

    I have 2 large worm bins in my office. They have both now wound up with many, many BSF larvae. I’m worried that when they turn into flies we’ll have thousands of BSF’s flying around the office. What can I do to prevent this from happening?
    Thank you!

    • September 15, 2011 at 12:38 pm

      Hi nancy,

      You can try removing the dark brown mature larvae but I’m sure you’ll miss many of them. The best method would be to move the bins outside. Good luck!

  • September 19, 2011 at 1:49 pm

    I was under the impression that only the dark grubs should be fed to chickens but I have fed them the lighter ones because they love them so much. Also my colony is in my compost pile and I don’t ever see dark ones. I have put a pvc pipe at an angle in there hoping to harvest some but that hasn’t worked. If they arn’t mature will they hurt the chickens?

    • September 21, 2011 at 6:06 am

      Hi Diane,

      All stages of larvae are fine as feed. The lighter juvenile larvae are preferred by a lot of animals, most likely because their “skin” is softer.

      You probably aren’t seeing the dark larvae because they migrate away from the pile as soon as they change whereas the juvenile larvae stay with the food. The dark mature larvae don’t eat and their only goal is to find a safe place to pupate. The dark color makes them harder to see and they tend to migrate at night.

      A ramp has very little chance of succeeding in compost pile. The larvae don’t/can’t seek out a ramp even in a well designed unit; ramps only work when they are placed in the path of larvae that are being channeled in a certain direction by the design.

  • July 22, 2012 at 12:55 am

    I also have made the 5 gal. bucket. Your instructions were super and clear. I used the material from a air conditioner for a filter and cut 1/4″ hardware cloth for the bottom and top of the filter material. I bought the BSF to put into the bucket but I think that I should have bought the younger ones as now they are in the middle of the filter waiting to turn into flies. I didn’t know that wood shavings should have been laid on the top of the hardware cloth. Also, I wasn’t quite sure what to feed the larvae. I don’t know if we have the BSF flies here in Boise, Idaho. I have kept the larvae in the house and the house flies and the fruit flies found the bucket and needless to say, the flies were driving us crazy. I had chicken skins in the bucket with fruit and it made quite a mess. So I tore it apart and separated the larvae from the filter material, added new material and cleaned the hardware cloth and tied the wire with string.. Going to try again with younger larvae. Please keep up the good work. I have enjoyed reading all of the questions and answers. Thank you so much for your help.

  • July 22, 2012 at 12:15 pm

    Hi Dee,

    I have doubts about there being wild BSF in Boise. You still might be able to establish your own micro population but without a native population you won’t enjoy the relatively easy BSF culturing which is possible in wetter, warmer climates.

    Having said that I will add that indoor cultivation is something I’ve never tried and wouldn’t recommend to the novice. If you want to pursue that approach you might want to register to our forum and share ideas with others who may have more experience.

    Under any conditions I wouldn’t recommend attracting BSF with animal protein. BSF will consume it, but there are many fly species that specifically target flesh and the waste will be overrun with those larvae as you’ve seen.

    One other point; if you try again outdoors you can deviate from the usual advice of keeping the unit fully shaded under certain circumstances. Since your climate is a bit cool you can use the sun to warn the unit in the early and late summer. The main thing to avoid is overheating so you would need to monitor that. On days when the high temps are in the 70’s or low 80’s a little morning sun will warm up the larvae and/or warm the waste you’re using to attract new adults.

    Thanks for your feedback and I hope you join the forum to share and to get more advice. Here’s a link: forum

Comments are closed.