Notes from Windward: #70

Bug Update

Bringing the Black Soldier Fly
operation online

Andrew, June 6:

     On May 28th we received this year's starter batch of Black Soldier Fly Larva (600 individuals) and meal worms (500 individuals) from our supplier Mulberry Farms. I have taken on this project as yet another aspect of the integrated food system envisioned for our critters. We will be using the Biopod this year for the start up colony. I have hopes to clean out the old BSF chest freezer unit at some point, but I am in no rush. Even when our colony grows large enough to warrant using the freezer, the Biopod is likely the place where we will initially establish our annual BSF colonies.

meal worm and BSF larva


     For more information about the Biopod you can check out the website for the Prota-culture team who have honed the design for harnessing black soldier fly larva. The web site has lots of good info, and links to other people who are experimenting with the BSF larvae.

     For more information about Windward's past experiments with the BSF's and other detritivorous insects, you can follow these links to previous issues of the Windward Notes.

Sustainability and the "Yuck!" Factor- how negative reactions to "yucky" bugs can limit ones options.

Magic Worms, sustainability's tiny alchemists. A good overview of detritivorous insect's role in our work with sustainable systems, and how we can harness the natural potential of BSF's in our pursuit of a sustainable agriculture. It also outlines the work done in creating a home for the BSF's to live in.

Magic worms: part two. This is a continuation of the first article, into the subsequent year with more general info about the BSF, and building the physical systems to house them.

The Propagation Greenhouse and overview of how our Prop-house was designed with BSF breeding in mind. Also good info about the life cycle of the critters.

Comments concerning previous Windward notes articles

     It is said multiple times in other articles that the BSF larvae can be used to harvest nutrients from the byproducts of animal butchering. How I originally translated these statements was that we will be able to feed the gastro-intestinal system of large animals to the larva. It is true that meat and animal products can be consumed by the larvae. But, there are several factors to consider when feeding animal products to BSF larvae.

     The larva cannot physically chew food. They have mandible type arms that can break off pieces of soft foods and direct it into the mouth. If the food is too tough for them to break off pieces, then it will have to decompose a little before consuming. Food such as cellulosic materials like leafy greens, dense starches like potatoes, and animal muscles are all tough for them to break down and consume without some kind of prior decomposition. Because it takes a little bit of decay for them to eat meat, there is also time for populations of nasty bacteria to form, and potentially liquefy.

      When the liquid is entered into the container it can quickly create a hostile, anaerobic environment for the larva. In order to mitigate negative affects of meat, other folks recommend that only a percentage of their diet at any given time be composed of raw meat, organs and guts of animals. And, to not put volumes of such products into the colony that cannot be consumed with one or two days. This can effectively reduce the potential for catastrophic putrification.

     Walt informed me that the colony collapse that occurred in another year was the result of overloading the larva by placing the body of a large animal into the BSF freezer unit. After opening the freezer and witnessing the results I agree with him. What I get from these observations is that, if you have a really massive colony going, you could probably throw the organs of a animal like a goat or sheep in with the larva and they would do fine. But it is very important to judge how quickly the animal will be consumed, and how it will physically affect the colony; i.e. will it seal off the bottom portion of the container and create and anaerobic environment? If so, break it up into smaller pieces.

[Walt: A key problem with using an old freezer as a BSF vault involved the moisture that accumulated as the larva broke down the wastes. It's easy to forget that animals are mostly water, and as the larva fed, they released the water incorporated in the tissues. This created a degree of dampness which set the stage for the development of anaerobic conditions.

     The moisture that condensed on the interior surfaces also enabled the larva to climb straight up the vault's vertical walls, something which defeated the collection ramp concept.

     The Biopod gets around this by installing a drain in the bottom center of the larva holding area. The drain is covered with a piece of the matting of the type that's used in the construction of drain fields for septic tanks. The mat allows moisture to drain out of the containment, while retaining the larva and solid particles.

     When we get to the point where we need something larger than the Biopod, we'll install a similar drain in the freezer chest and give it another try.


"If it isn't in the Notes, it didn't happen."

     With these articles from past issues of the notes, there is quite a stock pile of abstracted knowledge about the BSF's; however, after looking through the data that we have, I was left with many specific questions about the day-to-day management of the BSF system. Especially when in comes to establishing the balance of environmental and dietary factors at the onset of the colony. Opalyn expressed a similar sentiment in her work last year with the BSF larva. I feel as though without more detailed information, I am starting from scratch this year.

     This seems to be an essential part about having a revolving crew. Any information that is not recorded is essentially lost. Or as it has been put so succinctly, in the Spirit of Kaizen, I will attempt to fill in some of the information gaps by keeping a basic daily/weekly log of the BSF and meal worm systems. A hard copy of the data and conclusions will be available in our records, and I hope to be able to translate it into digital format for the notes. That way, others wishing to work with the BSF's or meal worms in the future will have access to a more concrete data set that is geared toward our land.

     My daily notes include:

  • Estimated temperature inside the colony,

  • Material inputs (food, water, etc)

  • How they respond to the inputs

  • Observations on the activity level and stage of larva progression.

  • Notes on specific problems

  • Any actions taken to remedy problems

  • And the volume of larva production

     As the colony stabilizes, these daily observation are becoming less frequent. But I want to keep track of how the larva respond to changes in the environment and types of feed.

Getting the BSF colony started

     I started out by laying down 4 cups of pizza flour. One of Windward's friends was involved in cleaning up after a truck wreck that contained a pallet of flour. The bags had been damaged in the wreck, so he loaded the flour into four 55 gallons drums and set them aside for us. It's more than 20 days later, and they have not yet consumed all the flour.

     The biggest problem I've encountered working with the flour is how maintain an adequate level of humidity. The pizza flour I used as a starting feed base is a sink for moisture. It keeps sucking up the ambient humidity created by whatever else I put in there. As the flour gets moist it clumps and becomes rather hard. And mold has begun to spread through it. I do not have any visible evidence that the BSF larvae can eat the hardened clumps of flour, but they have been found underneath the clumps eating the flour.

     I am not sure if the grey mold growing on the flour and vegetables is a bad thing. The mold has undergone boom and bust cycles and the larvae don't seem phased by it. I have not acted on it because there has been no ill affects that I can tell. It may be that the larva can actually eat the mold, while the mold consumes and softens food that the BSF's cannot break up and eat. In order to minimize mold, it is recommended that you only add as much food as they larvae can consume in a one or two days. I decided that I wanted to give them a base of food (4 cups of flour) to work from. This seems to have worked out well. But we will see how the mold situation progresses in the future.

BSF larva feasting on carrots and coffee grounds


     The way I originally dealt with the humidity issue is to add water once or twice a day with a spray gun. I moistened the walls of the container, stirred the contents of the Biopod while spraying. But, I soon got tired of doing this and tried adding root vegetables (mostly rotting carrots) that will slowly release moisture. This works fairly well, but it takes a long to for the larva to consume, and will not rot the way other food might and will continuously give off moisture.

     I have also read that the Black soldier flies do well with regular inputs of used coffee grounds. This appears to hold true. In the least, the grounds add moisture. They do, however, start to mold rather quickly, and there I have concerns that adding too much will make the environment overly acidic. I have added one pot of coffee worth of grounds every three days for the past week. The total volume of grounds is approximately 1/3 of the total volume of inputs, next to rotting root vegetables (potato and carrots), left over apple and pineapple bits, and the original pizza flour.

Meal Worms

     I am happy to report that the meal worms are doing famously! I started them off in rearing boxes that were purchased specifically for meal worms. The containers are common plastic storage tubs, approximately 2 feet by 4 feet by 6 inches deep. I filled the container with about 2 inches of pizza flour. I keep some moistened newspaper and cut up carrots on the surface of the flour for moisture.

mealworms working the flour


     The worms were added to this set up, and over several days I found a few dead worms. There bodies were black and hard, and I am unsure of why they died. But each day I added more moist paper and carrots until I stopped finding dead meal worms. It was at this time that I regularly found beads of moisture condensing on the sides of the plastic container. There is correlation between the relative humidity and finding dead worms, but I am unsure whether there is causation. More on this to come in the future.

     The meal worms now seem to be flourishing. During the warmer parts of the day they are very active and seem to be thriving off of the flour. They tend to congregate in the flour around the moist areas created by the paper and carrots. Supposedly they come to the surface to "take a drink" when they are thirsty. I don't know how they drink, but it is evident that they like to hang around the moisture.

     Everyday I find more of their casings, meaning that they are literally growing out of their skins. Eventually they will metamorphose into little black beetles. When this happens I will transfer some of the beetles into another rearing tray. They should then lay 200-500 eggs per beetle in the flour and start another colony.


July 6: Pupation well under way

     Happy to report that the Black Soldier Fly larvae and the Meal worms are doing wonderfully. As the days warm up they are becoming increasingly active, and both the colonies are starting to mature to the point of pupation.

     Exciting times! And also an opportunity to take the BSF larva animal feed system to the next stage.

     Black Soldier Flies - A little history to explain where we are at…

Black Soldier Fly pupae


     We do not have a native BSF population here at Windward. From what I understand, the winters here are too cold, and the summers too dry for the poor bugs. This makes our job a little harder, because we need to create a context in which the BSF's survive in an area where they otherwise would not be able to. We need to be able to put the colony into stasis for those cold months. From what I have been reading, there are three ways we can potentially do this.

     We can insulate a large colony so that the internal temperature of the mass of larva remains above freezing. The process of microbial decomposition, as well as the heat generated by the movement of the larva has been proven to be sufficient to keep a well insulated colony viable over an extended winter season. The biggest challenge that faces us now is having a large enough colony to generate the heat needed to last through the winter. We will need to at least triple the size of the colony before I think we can overwinter the larvae in the biopod.

     Another incarnation of the insulation tactic is to create a temperature and humidity controlled environment for the BSF larva. Essentially, expanding the insulation to a larger area than just the colony itself, and making the BSF's a part of a larger system. This is what the vision for our integrated aquaculture/hydroponic/greenhouse/refrigerator structure that we affectionate call "The Pearl".

     In The Pearl, the thermal mass of the fish tanks combined with the humidity created by evaporation and plant respiration, within an insulated greenhouse design, should (in theory) create a relatively warm and humid environment for the BSF colony to overwinter in. This is the final stage of the proposed system, but is not going to be ready this year.

     An interim step that I am experimenting with now is much simpler. It does not involve maintaining a colony outdoors over winter. Instead I am going to attempt to refrigerate BSF larva and eggs for an extended period of time.

     According to other research, BSF's in the larval stage can be maintained at temperature just above freezing. My guess as to the mechanism is that, as the temperature drops, the larvae's metabolism grinds to almost a halt.

     I have not been able to find definitive data on just how long they can stay in stasis. Some sources say up to a month, and others say for several months. I have also not been able to find any information about keeping BSF eggs in stasis. So, I will try it out and see.


Here come the Adults!
Creating a containment area for the BSF larva.

     One of the biggest problems that I will face in attempting to keep BSF alive year round is collecting their eggs.

an adult Black Soldier Fly


     The adult BSF

  • are small,
  • they fly,
  • they don't live long,
  • they can't drink and thus need a high humidity, and
  • they mate in flight while being directed by the sun.

     All of these things combined make it difficult to effectively contain them.

     What I am trying now involves a containment area made of a salvaged 25 gallon fish tank and a solid make-shift lid. The bottom of the tank is covered with torn up paper so the BSF larvae have a place to take shelter, and as a way to buffer the humidity. Some open top containers filled with water were added for humidity. Watermelon rinds were also added for humidity, as well as to see if the BSF larvae were going to eat them.

the inside the pupae terrarium


     In the corner there's a gallon jug cut in half. Over the open jug I placed a strip of corrugated cardboard folded accordion style. In the jug I put a gizzard from a recently butchered chicken, a rotting pear and some water melon rind.

     In theory, the flies will hatch out, be able to fly around inside the clear container and mate with each other while being oriented by the sun. Then, the females will be attracted by the putrescent material in the jug, and lay their eggs in the cardboard above it. The eggs are then concentrated in a package of cardboard to be refrigerated for a period of one month. At which point, we will see if the eggs hatch.

metamorphisizing pupae


     Right now I am transferring the mature "puparian" bsf larva that have climbed into bipod's collection bucket into the terrarium/fish tank. Once I start seeing live adult flies in the container, I will stop putting new larva in. This is mostly because if I open the lid they will probably fly away and we may never see them again.

Meal worms
(aka Darkling Beetle or Flour Beetle larva):

meal worm rearing tray


     A little more background about mealworms. They are part of the Darkling beetle genera, all of which are a sort of co-evolutionary species with humans. The larva of darkling beetles prefer to feed off of grain and various kinds of pulverized grass seeds. For a long time now these beetles have been hanging around humans, nibbling off the crumbs of their stores of grain and generally being a nuisance by contaminating the grain with their beetle wastes.

     As for our meal worms…they are continually growing as they devour the pizza flour that is being used as their primary food source. In the late afternoon the colony is hyper active. Most of the mealworms are now close to an inch long. They have all molted multiple times in order to grow to such a large size.

     Now that I have the system set up properly, and have stabilized to humidity and light issues by placing pieces of damp paper on top of the flour, all I really have to do is wait for the larva to pupate.

     Here is how studies have broken down the time scale for the average meal worm beetle's life cycle.

Egg: The eggs are white and between 5-10 mm in length. They hatch after anywhere from 10 to 12 days, but in a warmer environment average closer to 10 days.

Larva: I trust that y'all know what meal worms look like. If not, check out the previous bug update for a picture. Supposedly the larvae really like hot dry environments. But they require a source of water at least daily. I suppose in the wild they would be living in the grass and would be able to sip some dew every morning. Most sources say that a piece of apple or some cut up root vegetables work well. I have laid dampened pieces of feed bags over the flour. They seem to be doing fine with this set up.

     From hatching, the larva will increase in size, molting their exoskeleton to make room for each stage of growth. Some varieties will get up to one and a half inches long, ours are about one inch right now.

     The larva can live from anywhere between 120 to 540 days depending on food and environmental conditions. In the kind of set up we have that number should be somewhere in the 120-150 day range.

meal worms before and after molting


Pupa: Pupa are white in color and, as they complete the metamorphosis, will darken in color. They are reminiscent of a butterfly cocoon, and are thus easily distinguished from the larva. They hardly move for the duration of pupation. This process generally takes 20 days even in optimal conditions.

meal worm pupa


Beetle: The beetles are shorter than the larva, coming out of pupation about half an inch long. They are fairly common throughout the world. They can live for several months, and will continue to eat for the entire time.

adult mealworm beetle


     Once I have little beetles walking around I plan on scooping them up, and putting them in a similar container as the one I am using for the larva. The container will be filled with a small bit of flour so that the beetles can eat.

     The goal is to get the beetles to mate and lay eggs so that the flour/eggs can then be collected. Much like the BSF's, I am going to see if the eggs stay viable after living in the fridge for a month. Or if meal worms at any stage of larval development can survive refrigeration.

Notes From Windward - Index - Vol. 70