MAY 30

Today I harvested the first of the prepupal black soldier fly larvae (Hermetia illucens) from this year’s colony. At this stage their instinct is to leave the food source and find a suitable place to pupate. I don’t know much about this part of the BSF life cycle so I want to find out first hand. I put the harvested grubs (larvae) into a closed container and I’ll be observing their behavior and changes, hopefully until the point where they emerge as adults.

testing black soldier fly development

When BSF grubs enter into their final stage as larvae they undergo some interesting changes. They go from a pale “grub” color to a dark coffee brown, and their mouth is replaced by a hook-like appendage to help them crawl in search of a good pupation site. They also empty their gut and excrete an antibiotic, a behavior which I find fascinating. A veterinarian friend of mine wonders if animals that eat the final stage grubs might benefit from ingesting the antibiotic.

Update MAY 31

Yesterday I placed about 15 prepupal BSF grubs into a one gallon container with some leaves and grass. If you click the photo above to enlarge it you can see a few of them. I added a handful of sand to one corner of the container and the larvae quickly buried themselves in it. One entered the sand but came back out and settled under a leaf.

I found a great poster by the Swiss Federal Institute of Aquatic Science and Technology (eawag), which outlines the BSF life cycle. BSF LIFE CYCLE


They’re just laying there…


*tap tap tap*


I spoke with Dr. Olivier and he said that sand isn’t the best material for a pupation site. He recommended using sawdust to house pupae. He also puts some in the BioPod collection bucket to help keep it dry. He told me about a hamster bedding that works well, I think it was Aspen Bedding.

My pupae are still pupating…..


Still waiting!


Today I noticed adult BSF emerging from the pupae for the first time. It’s very possible that they started coming out before that but what can I say, I’ve been busy. :) I tried to photograph the process of the adults emerging but it happens very quickly. I checked on the pupae at one point and I noticed that an adult had it’s head out of the casing. I ran for my nearby camera and in the 20-30 seconds it took me to return the fly was already out and expanding it’s wings.

newly emerged black soldier fly

newly emerged black soldier fly 2

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21 thoughts on “Timing the transition-larva to adult black soldier fly

  • July 2, 2008 at 12:23 pm

    Hey Jerry, the BSF larvae you sent to me have started emerging as adults, also. I think the first one emerged about June 26th, and at least 2-3 others have become adults now. I’m keeping them in an inexpensive 10′ square screened gazebo to try to keep the adults close to the food source (and to each other).

  • July 2, 2008 at 2:07 pm

    Glad to hear it Jase, I hope they mate for you.

    Do you have any Barry White? :)

  • July 17, 2008 at 2:53 pm

    Hey Jerry, update? How long did it take for them all to emerge?

    What was the temperature while you were doing this? As I’m sure you know, temp makes a huge difference in how fast many insect species go through their cycles.

  • July 17, 2008 at 3:08 pm

    I have to admit that I didn’t keep close records on these pupae. The average daytime temperature was in the mid 80;s and the lows were in the low 70’s. I would estimate that there was a week long spread in the emergence of these adults, but I can’t be sure exactly when each one pupated. Some probably pupated before others. In the future I’ll run some more controlled tests.

  • March 12, 2010 at 6:47 pm

    We have been noticing a lot of these larva crawling through our house. I was not sure what these are until I found them on the net. I was curious on how they were getting in. I have traced them back to my septic tank out side where there are hundreds of them swimming around. They seem to find there way up the septic pipe and are exiting from around a perished rubber casket where the bowl connected to the pipe. I noticed these are found in compost heaps but how did they get into my septic system? Do you think this is a problem? Should I just leave them be or should I get rid of them?
    I would be interested in any comments. I could send a photo if you are curious as I.

  • March 12, 2010 at 6:57 pm

    Correction from my last message, they are the pupae not larva crawling through the house.

    • March 12, 2010 at 11:22 pm

      Hi Bernie,

      The only thing I can think of is that there must be an opening to the septic tank that is attracting the female BSF which are laying their eggs nearby. The newly hatched larvae are very tiny and are making it to the tank. When they have matured they instinctively crawl away in search of a pupation site and a percentage of them are using the pipe. I think the best solution is to make sure that the septic tank is completely closed to the outside which will prevent future larvae from entering. When we raise black soldier fly larvae they are relatively clean but since the ones you’re finding have been exposed to sewage you should definitely take steps to eliminate them from your septic system.

      I’m always interested in BSF photos, but I assume your identification of them is correct. BSF will process fecal waste and when outhouses were common BSF were often found inhabiting the waste. For this reason they were sometimes called “privy flies”. In the case of the outhouses the presence of the BSF larvae was mutually beneficial because they typically repel disease carrying fly species such as the common house fly. The life cycle and behavior of BSF results in them not being carriers of human diseases.

      Since you know that you have BSF on your property it should be easy for you to start culturing them if think you might be interested. Many people that read this blog will be envious that you have a known population ready to serve you. Good luck.

  • June 17, 2010 at 11:49 pm

    Hello Everyone,

    I have just started a few bins and they are doing pretty good. I was wondering if they need and balanced diet? I have feed them mostly meat and a little veggies.There’s still some solid stuff in there that’s old.I’m I feeding them to much ? Should it be totally liquid before I add more food.Thanks for your time.

    • June 18, 2010 at 9:22 am

      Hi Joe,

      Please be careful about feeding a lot of meat to your colony. It’s never a good idea to have meat sitting around rotting for days so if it isn’t being consumed by the larvae in about one day then I would cut back on the amount until new additions of it are gone within 24 hours. Spoiling meat is a good medium for growing botulism. This could be an issue for any animal that might eat the larvae raised on meat that developed this toxin. Processing meat is fine, but don’t overdo it; I would limit the percentage of meat to vegetable matter to about 20% just to be cautious.

      “There’s still some solid stuff in there that’s old.”

      I’m not sure what that means, but I would dispose of any animal product that remains uneaten after 24 hours.

      “Should it be totally liquid before I add more food.”

      I don’t think a BSF unit should ever contain waste that is totally liquid. Your BSF unit should have a drainage system that allows liquids to pass through quickly leaving the waste pile damp but not wet. A flooded BSF colony can become anaerobic which, if not corrected can lead to a crash of the system.

      Based on your comments I can’t imagine that your colony is healthy or balanced, and I don’t expect it to remain functional for long. I recommend that you; remove and dispose of any uneaten meat, reduce the quantity of meat that you process to 20% of the total waste, add shredded office paper, sawdust, or wood shavings to absorb excess liquids. Please keep in mind that any bad odors are sign that your system needs attention.

  • July 13, 2010 at 4:45 pm


    I read an Australian study that discovered that soldier grubs can break down meats faster then any regular composting bin if the % meat in the waste remains below 5%. The moment you add more than 5% per day of meats the meats seem to break down more slowly. At 10% meat per day there seems to be no difference between the grubs and the regular compost bin.

    However, those are daily percentages. If you add 10% one day and add no meat the next you should be fine. Therefore your notion of 20% seems logical, as it would take 4 days to brake down. Anything mor than 4 days can start supporting blow flies.

    I wouldn’t put any meets during bating.

  • July 15, 2010 at 8:02 am

    Firstly..well done on this site! Creative and inspiring! Another possibility is also not working with a circular bucket but a SQUARE plastic storage bin.Why bother you say? Answer = Because [theoretically at least,] you can run a square type configuration of any common straight plastic piping along the inside of the box without the problem of having to bend it to fit a round walled container, as you might with a bucket.You just get required length of hard type plumbing type piping to run the inside perimeter of the box, to make an internal square or rectangular “frame”.But using piping cut in half so that you have an open ramp effect.Basically you’re imitating part of the internal wall ramp of the new commercially produced BioPod Plus,[which, note,is also square,] but the bug “ramp”/escape highway is made from added piping [cut in half] rather than of course being moulded into the side of the container walls itself.This square [or rectagular..depending on shape of plastic box being used,] could then be “propped” on one side of the frame that, again it runs at an angle,simular again to the newwer BioPod Plus ramp internal configuration.

  • July 15, 2010 at 8:12 am

    Sorry if that last post was verbose or confusing.All I was trying to say is why not just get any old plastic storage type box and some rigid plastic piping and imitate what’s been done commercially internally with the new BioPod Plus.This [in theory at least,]should get round the problem of the fiddly bits with the current design (ie. funnels, floppy tubing and magnets and maybe all the fiddling and adjusting that that particular set up may involve.) I’ll try and see if I can post some sketches through..

  • July 15, 2010 at 8:16 am

    Has anyone tried using an old potato sack [you know the old fashioned material type,] as a bottom filter?

    • July 15, 2010 at 8:48 am

      Hi Simon,

      Thanks for positive feedback.

      Myself and others have worked with rectangular storage bins and pvc pipe ramps some of which can be found online. It can work, but in practice I think it’s more challenging to build than the bucket composter. The adjustments needed with the bucket ramp system are minor and only necessary once or twice a week usually. A sketch is a good starting point but the behavior of the larvae often causes unforeseen issues. The only reliable way to know if a design has merit is to test it with a colony. I look forward to more people working on DIY designs and I hope you have success with yours.

      A potato sack might work; I would probably try several layers and also loosely stitching them together.

  • August 14, 2010 at 7:33 am

    Hi,again.Point taken…However the new Biopod Plus is square/rectangular….

  • August 14, 2010 at 7:39 am

    Looks like I may be FORCED to build my own as there are currently no Australian distributers available [Circle 3 is,apparently looking for another OZ distributor.] I have yet to hear back from other US dealerships, but Catawba Coops wanted US$215.94 just for shipping, and the unit itself is “ONLY” worth US$189.50 = OUCH BIGTIME!!!

  • August 14, 2010 at 7:47 am


    I’m not sure you understood my point. I didn’t say it’s not feasible to work with a storage bin; in fact it’s the most common container used by myself and others. The only issue with them is that making a ramp system with rigid pipe takes a higher level of expertise than my bucket design. I’ve made very effective units with rectangular storage bins and someday when I refine the design a bit more and I’ll publish directions to build one.

  • August 5, 2011 at 5:52 pm

    I shore would like more info on achieving adult flies
    thanks to everyone who contributes

  • September 2, 2011 at 1:26 pm

    Great site. Lots of good information. My understanding is the life cycle of BSF is: eggs hatch in 102 to 105 hours (4 days and 6-9 hours). the larvae mature in about two weeks to 6 months determined by food availability and temperature. Mature BSF lives 5-8 days (lays eggs within 2-4 days of getting wings). Please, let me know of any observation contrary or otherwise.

  • September 22, 2011 at 11:20 pm

    I’m interested in maintaining a sustainable black soldier fly population for my eight chickens, but I’m wondering a) if a family of 3 and a baby who are mostly vegetarian (maybe 2 servings of meat a week) will supply enough proper food for this and b) how easy is it get them to reproduce? In what state do you obtain the flies, and is your system designed for sustainable populations?

    Great website, fascinating indeed,

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