Updated 2013/01/15

Indoor Black Soldier Fly Breeding II

I've tried to define any acronyms the first time they're used but here's a summary too:
  • BSF - Black Soldier Fly or Flies
  • BSFL - Black Soldier Fly Larva or Larvae
  • UCG - Used Coffee Grounds
  • CFL - Compact Fluorescent Light or Lights

This page presents my experiences in 2012 in chronological order with the newest information at the bottom. 2013 activities are here.

I've included links to some dates below. Clicking on the date at the beginning of each section will return you to this list.

If you have any questions or comments please e-mail me.

Following my initial experiment with Black Soldier Fly (BSF) breeding in captivity (link) I had about 200 newly hatched larvae. For this generation the design of some equipment was changed and materials repurposed. BSF larvae (BSFL) are known as escape artists so any design changes still had to be able to securely contain them.

As before, the larvae were raised in a 'rearing tub' constructed from plastic margarine type containers nested together. My previous rearing tub had problems with the drainage holes in the bottom clogging. This time I used a landscape fabric bottom as inspired by Heather Twist's 'Grow Cone' described in her blog post of 2011-09-28 : An escape proof home! The landscape fabric provides good drainage and also aeration from the bottom.

I used two 12cm (4.5") diameter containers - one cut off at the bottom and the other cut off about 3cm (1") down from it's rim to form a collar which nested inside the first. The landscape fabric 'pocket' was suspended from the rim of the first container and held in place by the collar. This collar allowed for a screened lid to be secured over the 'pocket' to prevent the larvae from wandering and provide ventilation to the top. The larvae and bedding/food rest in this 'pocket'.

The 'pocket' assembly sat inside a third larger tub which has a solid lid with pinholes for ventilation and to contain the larvae should they escape from the inner tub. This outer tub also captures any liquid that drains through the landscape fabric and helps maintain the highest possible humidity for the larvae. The inner assembly is easily removed to allow the outer tub to be emptied of any accumulated drainage.

The larvae were fed small amounts of used coffee grounds, used tea and kitchen scraps (fruit and vegetables). I did not feed any meat scraps to avoid potential odor problems.

The rearing tub was kept at about 24C (75F) which is less than optimal for larvae growth and it took over two months before they began to pupate.

2011/11/29 - At this point I set up a storage tote for the larvae to pupate in. The tote was placed completely inside a netting bag made from curtain sheers to contain any wandering larvae. The tote and netting bag were repurposed from the mating inclosure (link) I had tried previously. A zipper in the netting provides access. Split round foam pipe insulation secures the netting around the open rim of the tote as inspired by the bin described here and a solid cover over this helps maintain high humidity. The 53 Litre storage tote (58.4cm x 41.3cm x 31.4cm LxWxH) contains:
  • A 3cm layer of small animal bedding over 2cm potting soil on the bottom
  • A small container of sawdust
  • A screened container of water for humidity
  • A humidity meter
  • A wireless thermometer sensor

Initial Configuration Of The Pupation and Mating Bin.

Exterior of Pupation and Mating Bin
Changes from photo:
A sheet of clear plastic is used to cover the bin to let in more light.

The tote is kept at room temperature (21C/71F) and with the lid on the relative humidity stays between 80% and 90%. The humidity and temperature are recorded daily.

As the larvae had grown a larger rearing tub was constructed from 15cm (6") diameter margarine containers. In this version the landscape fabric 'pocket' is held in place by a lid instead of a collar. The center of the lid is cut out leaving only a narrow rim which allows larvae to crawl out of the rearing tub when migrating to pupate. This open bottom tub is nested inside a similar sized container and is easily removed to allow the outer tub to be emptied of any accumulated drainage.

The Larger 15cm (6") Diameter Larvae Rearing Tub

The Inside Bottom of The Larvae Rearing Tub
The larvae eventually shredded the landscape fabric and it was removed.

The rearing tub was set into the bedding on the bottom of the tote/bin so the tops of the tub and bedding were at about the same level. Later the rearing tub was temporarily placed inside a 4 litre ice-cream pail with a screen lid to allow counting of the number of mature larvae migrating to pupate. Any dark mature larvae that crawled out of the rearing tub into the pail were counted and transferred to the sawdust container daily. These larva usually burrowed down into the sawdust fairly quickly.

2011/12/26 - Over a period of two weeks 29 migrating prepupa were counted and the first fly emerged on this date. At this point the pail was removed allowing any mature larvae migrating to pupate to crawl directly onto the bedding. As of 2011/12/31 no other flies had emerged. I also discovered that larvae were finding a way under the landscape cloth in the rearing tub and becoming trapped. These four prepupal larvae were transferred to the sawdust cup from under the landscape cloth.

Posts in the Black Soldier Fly Forums (link) in late 2011 document that mating can be achieved in a fairly small space (storage tote size) using bright artificial lighting at 3500+ lumens. Lumens (link) are a measure of the "amount" of visible light emitted as compared to the more familiar Watts which are actually a measure of the power consumed. After a few more flies had emerged I experimented with several Compact Fluorescent Lights placed just over top of the bin to stimulate mating. I used lighting fixtures that I already owned so the setup is not optimal but is functional for testing.

I've had interesting discussions on forums (link) and (link) about sunlight and lighting, more specifically about units of measure for light. Please see my page "Lighting for Black Soldier Fly Breeding" (link) for information including the summary 'Lighting Used In Successful Indoor BSF Breeding Systems'.

2012/01/05 - About eight flies had emerged (it's hard to count moving targets) and I observed the first coupled mating pair. At this point there were Compact Fluorescent Lights rated at a total of 4100 lumens (two 1600 lumen 23 watt and one 900 lumen 14 watt) in reflectors immediately above the screen over the top of the bin. On average the lights were on three hours daily. Temperature at the top of the cone reflector maxed out at 51C(123F).

Lighting for the Bin
Compact Fluorescent Lights rated at a total of 4100 lumens
(two 1600 lumen 23 watt and one 900 lumen 14 watt)

Compact Fluorescent Lights From Below

The temperature in the tote with the lights on rises to a maximum of 30C. The lights are used with the lid off and the bin is misted with a spray bottle to keep the relative humidity above 30%. The humidity and temperature are recorded several times daily.

2012/01/06 - Another three dark mature larvae were transferred from the rearing tub to the sawdust cup on.

2012/01/07 - At least 11 flies that have emerged. Mating pairs have been observed several times but so far no egg clusters have been found. A small container of Used Coffee Grounds (UCG) and cardboard strips placed above the rearing tub have been provided as egg laying sites.

Mating Pairs
Photos Taken Through Netting (Curtain Sheers)

2012/01/08 - So far lots of mating activity but no egg clusters. About 15 flies have emerged and there's lots of activity when the lights are on. My bin sits close to where I work on my computer and sometimes the flies are loud enough to be attract my attention. I believe a lot of this is just male territorial displays but mating is also noisy with both flies buzzing loudly with their wings. It can also be quite a rough and tumble process which is, in certain aspects, as entertaining as TV wrestling so I set up my camera in the bin for a couple of hours to record the action.

I am not an entomologist but I don't believe any of the pairs in the video actually mated as those usually stay 'en copula' (coupled tail to tail motionless) for an extended period. I have observed a pair stay coupled this way for over an hour.

Although there are no 'en copula' pairs in the video there have been many on previous days and I'm still hoping to find some egg clusters soon.

2012/01/12 - Still no egg clusters to be found. There are 20+ flies now and lots of activity when the lights are on. I believe a lot of this is just male territorial displays as there are lots of flies in a small volume. This blog post on the North Carolina State University Insect Museum site (link) mentions that "The males wait for females at lekking sites that they defend against intruding males. When an intruder is spotted it will by tackled by the defending male." This certainly describes what I've seen where one fly grapples another in mid air then the pair drop to the bin floor with wings flapping madly. This activity can last a minute or more with the pair becoming airborne in short hops. It ends without the long coupling tail to tail which I'm assuming is actual mating.

So are these failed mating attempts or just male territorial displays?

Territorial Defence Or Mating?

As for the lack of egg clusters the females could be laying their eggs hidden elsewhere in the bin. Maybe there are just a lot of male flies in the bin. I still can't reliably determine their sex at a glance.

Looking back to my first experiment (link) it was three weeks from when I first observed a mating pair to when the first egg clusters were found. It's only been about a week so I'm still optimistic.

2012/01/22 - To raise the temperature inside the bin bottles of hot tap water were placed against either outside end. These bottles provided a consistent low temperature heat source which lasted a couple of hours and are changed out a couple of times daily. The cooled water was not wasted but was used to charge my toilet tank.

Later the bottles were placed under the bin in a space insulated on the bottom and sides so that they kept warm longer and all the heat rose to warm the bin bottom.

2012/01/30 - Finally an egg cluster! A relief after seeing mating (coupling end to end) on an almost daily basis but no eggs in any of the provided ovipositing sites. As mentioned above it is possible that the females could be laying their eggs hidden elsewhere in the bin but I have doubts that any newly hatched larvae from these would survive. I believe they require higher humidity than that of my bin or they will quickly dry out and die.

The provided ovipositing sites include the rearing tub and small containers of used coffee grounds and tea leaf cuttings from used teabags along with cardboard strips placed immediately next to these items. As with my first experiment this first egg cluster was laid in the container of used coffee grounds which is moist and humid. I've decided not to move the egg cluster into a warmer more humid incubation container but will see how the eggs fare as is.

As it turned out a check later the same day revealed that the eggs were hatching and many millimetre sized BSFL crawling around in the used coffee grounds. I'll leave them be to grow a little before adding both the larvae and UCG to the rearing bin. Although I've designed my bin to contain any wandering larvae I don't believe the young larvae will want to go anywhere as long as there's food and favorable habitat.

2012/02/01 Egg Clusters and Newly Hatched BSFL

I also vermicompost and have learned that you can't easily contain worms but rather you provide such an attractive habitat that they don't want to leave. I believe the same thing applies to BSFL up to the age when they seek a site to pupate.

The older larvae in the rearing tub have managed to shred the landscape fabric to the point where the tub contents were falling into the lower drainage collection tub. This was cheap quality fabric purchased from a big box store and I believe that a better quality product might survive longer. I've removed the remains of the fabric after disentangling several large larvae so the contents are now in a normal tub with no drainage. I don't think liquid accumulation will be a problem as there is a lot of evaporation under the lights used for mating.

2012/02/09 - About five egg clusters were deposited in the cups of UCG over a period of less than a week then nothing since. A couple of these clusters yellowed over time and did not appear to hatch. I think this might have been caused by being in direct contact with the moist UCG. It would have been better if the eggs had been laid in the flutes of the cardboard provided but the BSF are not following the plan. No eggs have been laid in the cardboard to date.

The container of used tea cuttings was removed and replaced with two more of UCG. These containers, the rearing tub and the cardboard strips are all checked daily. No egg clusters have ever been observed anywhere except in the original UCG container. Despite this, newly hatched BSFL have appeared in the rearing tub and both of the other containers of UCG. I'm not sure how they got there but there are several possibilities:
  1. Eggs were laid unobserved at these sites
  2. The newly hatched BSFL migrated from the first container of UCG
  3. The newly hatched BSFL migrated from eggs were laid unobserved elsewhere in the bin

Before this I had doubts that any newly hatched larvae would survive migrating across the relatively arid bin bottom. If the females are ovipositing in small animal bedding it would explain a few things.

Update: Another possibility - The BSF had me fooled. I was digging around in one of the containers of UCG a few days later looking at the larvae and discovered a clutch of eggs which was completely below the surface and hidden from sight. I thought they always laid their eggs on the sides of the containers or on the surface of their food but they proved me wrong.

The population of BSF peaked between 25 and 30 but has declined to about 15. There are still a few large white larvae in the rearing bin 45 days after the first flies emerged. All of this generation are from eggs laid around the end of September 2011.

2012/02/15 - As the larvae in the containers of UCG had grown to about 4mm they were transferred to the rearing tub. The entire contents of the containers were dumped and flushed with rain water to insure that all larvae were transferred into the rearing tub. The containers were also left outside over night in -10C temperatures. This was done so that when the containers were refilled with UCG and returned to the bin any new larvae that appeared would be from new clutches of eggs.

There was a large dark mature larvae in one of the containers. It must of migrated out of the rearing tub to pupate and found it's way into the UCG. I transferred it into the sawdust container.

All of the strips of cardboard from the bin were moved to a holder immediately above the rearing tub.

2012/02/15 Cardboard strips above the rearing tub.
The scallops around the rim allow the larvae to exit to pupate.

No eggs have been laid in the cardboard to date but I think I've figured out why. In the research published from the SE USA it was noted that BSF do not deposit their eggs in wet material and the attractants used were purposely kept wet to promote ovipositing in the flutes of the cardboard. The UCG I've been using is dry enough that the BSF were ovipositing in it. To test this out I've outfitted two of the containers with cardboard on the underside of their lids and added enough water to the UCG to make it soupy.

2012/02/15 Cardboard on the underside of the lids
and the container of soupy used coffee grounds.
The container (a jar lid) is 83mm in diameter & 29mm deep.

2012/02/18 - The population of flies has rebounded to 25+ and there are at least a couple of new egg clutches in one of cups of drier UCG. My test with cups of soupy UCG has not produced any eggs in the cardboard under their lids. However there was a large dark mature larvae in each cup this morning. There's a discussion on the Black Soldier Fly Forum (link) about the possible attraction by mature prepupal larvae for a humid environment.

As winter marches toward spring the sun now shines in my east facing windows for a few minutes each morning. I've noticed that with the lights off the BSF gather on the side of their bin closest to the window even though the sunlight did not touch the bin. I put up a temporary shelf beside the window and put the bin in sunshine one morning. The BSF were stimulated by the sunshine in the same manner as the artificial lighting. No surprises there as they did breed in sunlight in my experiment last year. I'll move the bin beside the window soon and wean the flies off artificial lighting for this season.

2012/02/22 - In the test with cups of soupy UCG no egg clusters have been found in the daily checks but this morning one of the containers was swimming with tiny BSFL. I think I may give up on the cardboard and trying to determine the rate ovipositing. The current population of flies is at least 29 and mating is still being observed.

I found some hard dog food on a close out sale and have started to feed that to the rearing tub. The BSFL seem to be thriving and there are a variety of sizes in this generation.

2012/02/22 Varying sizes of BSFL in the rearing
tub. The largest are about 12mm in length.
The round pellets are moistened hard dog food.

2012/02/26 - Still no eggs to be found in the cardboard strips but this morning I removed a pupa from one of the larger flutes and several others looked to be similarly occupied. I guess the mature larvae find them to be a good place to pupate.

The larvae seem to like the dog food. I've been feeding 20 pellets (~9 grams) every second day. The fly population remains between 30 and 35. There are new larvae in each of the four cups of UCG with the most in the 'soupy' cups.

2012/03/02 - Finally found a clutch of eggs in a flute of one of the strips of cardboard in the 'egg trap' above the rearing bin.

2012/03/02 A clutch of eggs in a 3mm flute.

I'm also experimenting with a small tube formed of window screen as suggested by Tarvus (link) of 'Bug Barracks' fame.

2012/03/02 Egg traps (cardboard and screen) above the rearing bin.

The latest incarnation of the rearing tub (shown above) has more of the surface covered to reduce evaporation and keep the contents moist. I emptied the four UCG cups with larvae into it today and have set the cups outside to freeze/sterilize overnight. It is getting full and I'll probably replace it with a taller version at some point.

The 'egg traps' are now on a removable holder which just sits on the rearing tub cover. This makes it much easier to remove for checking than the previous version which snapped onto the rim of the tub.

The fly population has risen to 40+. They're fairly easy to count when the light is dim as they are sitting still. Usually they only fly when the lights are on or if the sun is shining into the room. A few of the dead ones have ended up being consumed by the larvae.

2012/03/05 - There have been another three clusters of eggs laid in the cardboard egg traps in the last three days. I have not put the UCG cups back into the bin and this may be promoting the use of the egg traps. None of the four egg clutches have hatched out yet. It will be interesting to see if they'll hatch successfully in the lower humidity of the bin which can drop to 30%RH with the cover off and lights on.

So far no eggs have been laid on the small roll of screen and the fly population is approximately 30.

The rearing tub contents remain soupy after the addition of the UCG and the water used to rinse all the larvae from the UCG cups. There is a great variety in the larvae sizes with the largest being about 20mm.

In the 14 weeks since the rearing tub was placed in the bin no larvae have ever been observed climbing the walls of the bin or caught between the bin and the curtain sheer netting. My assumption is that the prepupal larvae that are migrating out of the rearing tub are finding the bin bottom a suitable place to pupate and don't try to go any further.

2012/03/07 - The rearing tub was getting full so the larvae and substrate were transferred into a larger (1550cc vs 850cc) container. There are a lot of larvae in the 15-20mm size range.

2012/03/07 Moving into larger accommodations.

I purchased an indoor/outdoor thermometer and installed the wired remote probe in the rearing tub. It indicates that contents of the tub (larvae and substrate) are about 2C above the ambient temperature of the bin. Others have documented the heat produced by the larvae. From ESR International (link):
"The difference in temperature between inside and outside the unit can exceed at times 82F or 45 C"
See under What Happens in Winter at that link for a graph and some other information about insulating an outdoor system for use in the winter.

In a system more similar in size to mine another person (link) reports temperatures of 43C between the maggots versus a room temperature of 21.6C.

2012/03/09 - I am officially abandoning trying to keep track of the ovipositing rate by counting clutches of eggs. Removing the egg traps for checks was causing mortality to some newly hatched larvae and also allowing a few flies to escape. I was finding that when the holder was moved a lot of 1 - 2mm larvae from under the bottom of the holder were being crushed outright or were falling off onto my work table.

For the record there were about a half dozen clutches of eggs found in the egg traps in a week. The distribution between being deposited from the top or bottom was about even. No eggs were laid in the small roll of window screen.

The cardboard strips and holder will remain in place as they're definitely being used by the female flies (and by a few larvae for pupating) but the small roll of screen has been removed. The cups of UCG will not be put back in the bin for the time being as there are more than enough new larvae hatching from the cardboard egg traps.

The population of flies has fallen to about 22.

2012/03/13 - A bit of a special day as this was the first time I've been able to observe a female BSF ovipositing. She deposited her eggs into the top of a 5mm flute of a cardboard strip in the egg trap above the rearing tub.

The population of flies has dropped to about 13. This may represent the die off of the last of the flies from eggs laid last fall. The rearing tub is teaming with larvae of many sizes and some of these should start pupating soon.

This latest incarnation of the rearing tub is doing fine without any provisions for drainage. In fact evaporation and consumption by larvae are enough to require water to be added regularly to prevent the tub contents from drying out. There is very little water content in the materials being fed (mostly dry dog food) which is normally the major source of water in bins.

If the sun is shining the bin is moved to a window shelf and the artificial lights are not used that day. Otherwise the lights are only used a couple of hours daily.

After raising BSF in a transparent bin for the last couple of months I see that the flies do take in water and defecate (all over the walls of the bin). It appears they have a functioning digestive track so it may be the case that they can feed as flies. Breeding systems documented on the web do not feed the flies as they will reproduce given only water as stated below:
"Black soldier fly adults provided water, but not food, have short lives (10 to 14 d) (Tomberlin et al. 2002), but are still able to reproduce in a colony (Sheppard et al. 2002). It is hypothesized that adults in the wild may not need to feed but rely on energy stored in their fat body during the larval stage (Tomberlin et al.2002), which may explain their short life span." Tomberlin and Sheppard 2002
They may not need to feed to reproduce but it makes one wonder if feeding the adults might offer an advantage by allowing them to breed longer.

2012/03/16 - My first attempts to keep the humidity high in the bin and provide water for the adult BSF had unintended consequences. It turns out the BSF are not the most skillful fliers in the insect world and they would often end up landing in the open dish of water and drowning. I added a screened lid to stop the carnage but then the flies could not access the water. My solution was to use cotton strips to wick the water up to where the flies could get at it. In the present design the screen is replaced by a solid lid with a slit for the 'wicks' which stay wet and allow evaporation into the bin.

The flies seem to like resting on the wet wicks so I believe they're taking in water. I also mist the bin daily with a spray bottle for both humidity and to provide the flies with another source of water.

Water Container Parts
Lid With A Slit, 850cc Margarine Tub & Cotton Strips.

Tub Filled To 3cm With Rain Water, Cotton Strips Soaked In Water
Then Passed Through Slit In Lid.

Cotton Strips Are Folded Over To Create A Double Layer.

The population of flies has dropped again to about 9 only a couple of which were flying today.

2012/03/19 - I've been pleased with the operation of my bin and especially how the larvae seemed content to pupate on the bottom of the bin. I had not seen even a single larvae climbing on the walls of the bin until yesterday. Then in a single day I first saw a single larvae on the wall of bin and later two more between the exterior of the bin and the netting which incloses the bin. All of these were returned to the bin bottom but this morning I found a single larvae on the floor below the bin.

So why now? I'm guessing that it was a combination of factors:
  • The bin was in the sun with the cover on creating condensation on bin walls from high humidity allowing climbing.
  • The rearing tub was up against the wall of the bin allowing the larvae exiting the tub to crawl directly onto the wall instead of falling to the bin bottom.
The netting is repurposed from the mating inclosure (link) I had tried previously. It's basically a tube 152cm in length with open ends and a stapled fold-over seam. A short zipper on one side provides access. For the present system the bin was placed completely inside the netting with the zipper across it's top. Both open ends were then rolled up and secured. The netting was also secured around the top rim of the bin with a collar of split foam pipe insulation and bungee cord.

I had thought that netting being secured in this way would keep the BSFL inside the bin. Even past the barriers around the rim there are no obvious holes in netting so I'm not sure how the larvae found on the floor got out. It may have even got out of the top of the netting and crawled/fallen to floor. The BSFL have me outsmarted again.

Going forward I'm going to try to prevent condensation on the walls of the bin and keep the rearing tub from touching the bin walls. If that fails I may even power up the 'electric fence' located below the rim similar to what I tested last year (link).

The fly count was only six today. The picture below shows part of the egg trap from a couple of days ago. It gets the larvae coming and going.

Before And After Larvae - Eggs And Pupa

2012/03/24 - The second generation of larvae are starting to pupate in significant numbers. I had initially considered adding ramps to the rearing tub to aid larvae migrating to pupate but found that they were not required. The larvae had no problems climbing out of the rearing tub (link) probably due to condensation on the tub walls.

Over the past week I was able to observe several dark mature larvae climbing to the rim of the tub. Most then fell to the floor of the bin (about 8cm) and quickly buried themselves in the small animal bedding. Some larvae also hide under the base of the egg trap holder on the lid of the rearing tub. These are transferred onto the floor of the bin daily.

Remember that this system is not designed to funnel the migrating larvae into one spot for harvesting. As long as they can exit the rearing tub to pupate on the floor of the bin everything is good.

There may be a concentration of pupae in the corner of the bin where the rearing tub sits. That's probably not a problem but I may relocate it and the water container to the center bin for several reasons:
  • It might help to prevent migrating larvae from climbing the walls of the bin if they have to cross an expanse of prime pupation material first.
  • Quite a lot of the adult flies seem to get themselves trapped in the corners behind these and die. BSF are not the smartest of insects so they might die there anyways.
  • Easier access for cleaning of the walls of the bin.

Larvae are now regularly getting caught in the netting surrounding the bin. These are transferred back to the floor of the bin daily. The fly count was five today.

I'm now feeding the rearing tub three slices of banana and 25 pellets of dog food on alternating days. If the sun is shining the bin is moved to a window shelf. Otherwise the artificial lights are used for a couple of hours.

2012/03/28 - The crawl out of larvae from the rearing tub continues. Over the last week 36 larvae were found between the base of the egg trap holder and the lid of the rearing tub. These were all moved to the bin floor and modifications were made to prevent the larvae from collecting at this location. The lid was removed and the egg trap holder now sits on supports suspended above the tub.

Retrieving wandering larvae from the netting 'bag' which incloses the bin has become part of the normal routine. So far only six larvae have crawled out of the bin to become trapped in the netting but I've also found three other larvae outside of the netting. I don't believe these are getting through the netting but that most have fallen out unobserved while the netting was opened to retrieve the others. Also one may have hitched a ride on the egg trap when it was removed for checking.

Larvae looking for a way out
These two have climbed out of the bin and are trapped in the end
of the netting 'bag' where it has been twisted, folded back and
secured with an elastic band.

Obviously the collar of split foam pipe insulation and the bungee cord securing the netting are not stopping the larvae. However they do hold the zippered opening in the proper position and stop the flies from getting trapped between the bin and netting.

The netting seems to work well in catching the bin escapees but I need a better method of retrieving these larvae. The bin sits supported at either end and the larvae sometimes collect at the low point in the netting below the middle of the bin. To open the end of the netting the bin has to be repositioned which is difficult to do without crushing the larvae.

The fly population has fallen to just four and will probably remain low for a few weeks until the new generation of pupae begin to eclose and the flies emerge. The absence of flies should allow for removal of the netting for some cleaning and maintenance.

Pupae and old pupal cases (puparia) left after the flies emerge (eclose)
The rearing tub with egg trap and water container are visible in the
background. The wire on the left side is for the temperature probe
in the rearing pail.

While the netting was opened to retrieve an errant larvae it gave a good view of pupa up against the end of the bin (see above). The concept of using small animal bedding overtop of potting soil was to simulate leaf litter on the ground. The larvae seem burrow down to the bedding/soil interface to pupate which is the same as was observed in last years experiment.

2012/04/04 - The BSFL are indeed proving to be escape artists. Since the last update a couple more found a way out of the netting bag possibly through the stapled fold-over seam. In an effort to prevent further escapees this seam was folded over a second time and stapled again on a tighter spacing. Also the bin was built with an electric fence but it had never been used until now.

The fence was inspired by a worm fence developed by Brain Travis as shown in this video (link) and tested on BSFL last year (link). It uses strips cut from a roll of wide aluminum tape instead of the narrow copper tape in Brain's. The fence consists of two narrow strips of the conductive tape separated by a small gap and situated on the inside of the bin just below the rim. The strips are connected to a small 9 volt battery and any larva which touches both strips at once completes a circuit receiving a non-lethal shock.

To use the fence inside the netting bag the power leads were extended and routed through the zippered opening alongside the wire for the temperature probe. The battery was secured to the outside of the bin under the bungee cord.

Larval Retention System (Electric Fence)

So far so good. In the two days since the fence was energized no larvae have been found outside of the bin (in or out of the netting bag) as compared to six found in the two previous days. Battery voltage has remained steady at 9.15VDC so there is no evidence of partial shorting due to the high humidity in the bin.

As mentioned previously the egg trap holder now sits on supports suspended above the rearing tub to stop larvae from collecting under it. However, the holder has a 1cm square channel in it's base and the larvae are now collecting in this small space. I pulled out eight largish larvae from there today and there were more I can't get at. I am concerned about larvae becoming trapped here as they probably won't be able to pupate successfully.

The population of flies is up slightly to seven.

2012/04/11 - The electric fence is working well and no larvae have been found outside of the bin (in or out of the netting bag) in the last week. Battery voltage has only dropped from 9.15 to 8.96 VDC.

Some prepupal larvae are regularly collecting under the rearing tub which has a 12cm diameter base and weighs 1.36 kilograms (3lbs). It sits on the bare dry bottom of the bin with only a tiny scattering of dirt under it which must allow the larvae access to this very tight space. Again my concern is that the flies won't be able to get out when they emerge (eclose). At first I manually moved these onto the small animal bedding where they burrowed down out of sight. Later I found if the rearing tub was removed for a few minutes the larvae would crawl into the bedding on their own to get away from the light.

Larvae Of Varying Hues Under Rearing Tub

The population of flies has risen to 12. With this low population there have not been any new clutches of eggs in quite a while but there are still many 5mm sized larvae in the rearing tub.

2012/04/18 - The electric fence continues to work well and no larvae have escaped from the bin in the 14 days since it was energized. I have been able to observe several larvae trying to cross the fence without success. Some even raise up their upper body seemingly trying to arch over the fence. Battery voltage has remained steady at 8.96 VDC over the last week.

The population of flies has rebounded to about 30 and they're mating again. No obvious clutches of eggs yet but the egg traps haven't been thoroughly checked recently.

2012/04/26 - The battery drain for the fence seems to be very minimal which makes sense as the circuit only closes when a larvae touches both strips at the same time. Battery voltage has only dropped from 9.16 to 8.93 VDC over 24 days. No larvae have got past the fence during this period. Some even raise up their upper body seemingly trying to arch over the fence but fall back to the bin bottom.

An adult BSF and a pupa turned up in my worm bin this week which is also totally inclosed in netting to control fungus gnats. It's not likely that the fly would be able to get inside the netting. Some pupa from last years experiment which appeared to be dead (dried out) were disposed of in the worm bin in November 2011. It seems probable that some of these were still viable and are eclosing now.

The population of flies remains at about 30 and there are newly hatched 2mm larvae on the egg trap holder. The cardboard strips of the egg trap were replaced with new ones. The old strips had several clutches of eggs some of which were yellowed and had either hatched out or were not viable. The strips were put in a sealed margarine tub along with a cup of wet UCG and new larvae were seen in the UCG after a couple of days.

2012/05/03 - The system continues to operate well and the BSF are thriving. The rearing tub is almost full but many mature larvae are exiting to pupate on the bin bottom. Larvae are fed pellets of dog food and slices of banana on alternating days. The bin is moved to a sunny window for a few hours daily when the weather cooperates.

The population of flies has risen to over 40 but there have been no clutches of eggs laid in the new egg traps put out last week.

There are many small larvae in the second tub with the old cardboard egg traps. These have doubled in length to 2-3mm and will be left where they are to grow larger. They are feeding off a cup of soupy UCG with a slice of banana. This sealed tub is kept warm on an upper shelf in a closet.

The electric fence's battery has only dropped 0.43 volts or 4.7% over the past month as shown in the chart below. No larvae have got past the fence during this period.

Battery Voltage Drop Over a Month

2012/05/14 - Immediately after my last report two larvae got past the fence and were caught in the netting bag inclosing the bin. A lot of material has coated the walls of the bin since January which may have partially insulated surface of the tape strips protecting the larvae from shocks. This material is probably excrement from the flies and larvae. The walls of the bin including the aluminum tape strips were cleaned. A couple of days later when the bin walls were very wet another two larvae got past the fence but no more have in the past week.

A very small section of one of the aluminum tape strips has lifted in one corner which may be allowing the larvae to get underneath. Repairing this while the bin is active will be a challenge and I may just push a couple of bins through the tape into the bin wall to block the opening. The pins should be conductive allowing the circuit to be completed if a larvae is touching them and the second tape strip.

It may be that the dropping battery voltage is reaching a level where the larvae can tolerate the shock. I have a "wall wart" transformer from a discarded battery charger that outputs 9.47VDC which could be used but the battery is preferred because it allows the bin to be easily moved. The battery voltage is presently 8.74VDC.

Another four flies have appeared in my worm bins in the last 10 days. As explained previously (link) these probably are not escapees from my BSF bin. Unfortunately three of these were caught in sticky traps and only one could be transferred to the BSF bin.

The larvae in the second tub with the old cardboard egg traps have grown in length to 3-5mm and will be left where they are to grow larger. They are still feeding off the original cup of soupy UCG and slice of banana. This sealed tub is kept sealed on a warm upper shelf in a closet.

2012/05/22 - The fly population has been between 25 and 30. They are very active in the sunshine when the bin is moved to sunny windows in the morning and evening. A couple more larvae got past the fence in the last week but did not escape the netting. I should know by now not to think that I've got that problem licked but it's encouraging that the additional work on the seam appears to be working. The battery voltage is presently 8.64VDC and it will be replaced shortly.

Female Ovipositing Between The Cardboard Egg Traps
and Plastic The Holder

The larvae in the second tub with the old cardboard egg traps are doing just fine. Many have grown to almost 1cm and will be left where they are feeding off a cup of soupy UCG with a slice of banana. This sealed tub is kept warm on an upper shelf in a closet. I've placed another cup of soupy UCG in the bin and will move it to a separate tub when it has some larvae in it.

2012/05/31 - The population of flies has grown to 45+ in the last week. The cup of UCG in the bin has several larvae ranging in size up to 10mm+. A clutch of eggs was laid on underside of this cup and it was moved into a sealed tub with the cup propped up off the eggs. This tub along with the other which has the old egg traps will serve as backup populations in case something happens to the main bin. The larvae seem quite happy in these sealed tubs while they're small. As they grow and reach about 15mm in length they'll be transferred to the rearing tub in the main bin.

The performance of the fence has degraded over the last month and a few larvae were able to escape from the bin on six occasions. Only one larvae also got outside the netting.

Fence Voltage VS Escaping Larvae
A new battery was installed on day 52

I think there are several contributing factors some of which I've mentioned previously:
  1. Material deposited by the flies and larvae on the bin walls and the fence tape may insulate the larvae from shocks.
  2. The foil surface of the conducting tape is delaminating and coming off.
  3. The adhesive backing of the tape lifted from the bin wall in a small area.
  4. Declining battery voltage reached a level where the larvae can tolerate the shock.
Cleaning of the tape strips in response to item 1 may have contributed to item 2. The conductive aluminum foil is very thin and doesn't stand up well to any abuse. Copper slug tape might be thicker and a better choice. Another possibility is using wire which could be 'welded' to the bin wall with a soldiering iron. In any case replacing the fence while the bin is active will be a challenge.

The high humidity (80%+) in the bin may also have contributed to items 2 and 3. Item 3 was repaired by using a tumbtack to hold down the tape strip.

To solve item 4 the battery was replaced with a new one. A small "wall wart" transformer that outputs approximately 9VDC could be used but a battery is preferred because it allows the bin to be easily moved.

2012/06/23 - A few changes have occurred over the last three weeks. The performance of the electric fence continued to degrade and many larvae have got past it including 20 on one day. Retrieving wandering larvae from the netting 'bag' which incloses the bin is again part of the normal routine. A few larvae also escaped from the 'bag' on one day when an elastic closing one end came loose.

I am looking at a passive barrier (link) which works by breaking the surface tension of water which the larvae need to climb smooth surfaces. So far I haven't been able to find a similar product locally. Another possibility would be rebuilding the electric fence using wire which should be much more durable than the foil tape.

The original rearing tub was full to the brim. It was removed from the bin and placed inside a closed pail with a vented lid which is stored in a warm location. As the larvae mature and crawl out to pupate they are trapped in the bottom of the pail and then are manually transferred back to the bin. Once all of the larvae are gone the tub will be emptied and cleaned to be used again.

Larvae from the two external rearing tubs, and the UCG cup from the bin, were combined into one tub which is now in the bin.

For the summer the tub of water used for additional humidity has been removed and the use of bottles of hot water for supplemental heat has stopped.

It's now been a year (link) since I purchased the initial batch of BSFL to start this experiment. So far so good.

2012/07/31 - The bin population is thriving while larvae are still maturing in the original rearing tub which was moved to a separate container five weeks ago. These are transferred daily to the new rearing tub in the bin. The newspaper liner from the pail is transferred too and is eaten by the next day.

Maturing Larvae From The Original Rearing Tub
They seem to get larger (+25mm) on a diet of dogfood and are exiting the tub before turning dark.

Discovered another larvae living happily in one of my worm bins this past week. As explained previously (link) these probably are not escapees from my BSF bin and I also don't believe they are from a clutch of eggs as there would be a lot more than the few I've seen to date. The worm bins are out on a balcony for the summer so the larvae are able to survive outside here at least until autumn.

The bin bottom is now covered with a layer of dead flies and old pupal cases (puparia) left after the flies emerge (eclose). At some point these will have to be cleaned out while keeping the bin in operation. One option is to transfer these along with all of the paper bedding with any pupa into a second bin and replace this with new bedding. Option two is to move the rearing tub and live flies into the second bin. In both options the old material would be kept for a couple of months and any flies that emerged would be transferred back to the active bin. I'm not sure which would be easier.

My original bin lid was opaque and loose fitting (definitely not larvae proof). I would like to get a small sheet of rigid clear acrylic to use as a lid which would be more transparent to lighting than the net. Installed properly it should also be larvae proof and the net would no longer be needed.

2012/08/28 - The BSFL population in the bin continues to breed and reproduce well. The bin is in sunshine a couple of hours most days and is misted daily to 'water' the adult flies. Although the 'electric fence' is inoperative only a very few larvae have crawled out of the bin over the last several weeks. A couple more adult flies have got past the split round foam pipe insulation securing the netting around the open rim of the bin and became trapped between the outside of the bin and the netting.

The active rearing tub is filling despite the feeding rate being halved and there are hundreds of active larvae. I will likely start another new tub soon then move this one into the pail to isolate it from any gravid female flies. As before, the larvae will be transferred back to the bin as they mature and crawl down to the pail's bottom.

The last larvae from the old rearing tub matured last week. This was nine weeks after that tub was isolated from the bin. Towards the end the feed was not consumed and began to mold. The resulting BSFL castings were very foul smelling. At the bottom it was dense, almost dry and grainy like sand. This probably was bone meal from the dog food I was feeding the larvae. While left outside to dry several house flies laid eggs in the castings so due to this, and the smell, this material was discarded rather than being placed in my worm bins.

Speaking of worms, a couple of days ago I harvested some vermicompost from one of my worm bins. This material was quite wet and was set aside to dry. It was placed inside a netting bag to trap any fungus gnats which also happened to trap a couple of newly emerged BSF.

This was really a surprise to me. I have found BSF in the worm bins before (link) and assumed they were from some dried out pupa from last years experiment were disposed of in the worm bin in November 2011. It's highly unlikely that these flies are from those pupa at this late date. A few larvae have since escaped from my bin and I very occasionally capture a loose fly I think came from these but haven't seen any for months. It seems unlikely to me that any escapees could mate unobserved as they end up buzzing at a sunny window. Also, the worm bins are totally inclosed in netting which would prevent ovipositing inside. For now it's a mystery how the larvae are ending up in the worm bins.

On a subject related to my escaped larvae I recently found an old pupal case (puparia) underneath a cardboard box. There was no sign of the eclosed fly so I'm assuming it was able to crawl out from under the box. Previously I've worried that pupa were getting into spots in my bin where the emerging flies would be trapped. I even mounted the rearing tub up on 'feet' to guard against this. If a fragile newly emerged fly is able to crawl out from under a cardboard box then 'trapped' flies are probably not a problem.

2012/09/28 - The BSFL population in the bin continues to do well and is misted daily to 'water' the adult flies. The 'electric fence' remains inoperative but almost no larvae have crawled out of the bin over the last couple of months. I'm not exactly sure why but it is a welcome change.

With the return of fall and cooler temperatures the use of bottles of hot water for supplemental heat has been resumed. These bottles are placed under the bin and are insulated all around except for the top so the heat is directed up to the bin bottom. Even with the shorter days the bin is still in sunshine a couple of hours most mornings so the lights are not required for now.

The rearing tub was almost full so 75% of the contents were put into a second tub which was isolated in a pail with a vented lid and stored in a warm location. The isolation prevents any additional eggs from being laid in the material. These larvae are fed regularly and as they mature and 'crawl off' to pupate they will be transferred back to the main bin.

Larval Maturing Tub and Pail
The pail has a vented lid and newspaper bottom liner.
The tubs sits on feet to allow the larvae to easily crawl underneath.

Cleaning and renovation of the bin will occur in the next month or two.

2012/10/30 - Here's another in what are turning out to be monthly updates. I was away for 10 days early in the month and was worried how the colony would fair without daily attention. A smaller version of the water tub with cotton wicks (link) was used to provide water for the flies and keep the humidity high in the bin. Both the rearing tub and the tub in the pupation pail were fed a large slice of raw potato as 'vacation food' (link).

The colony survived just fine in my absence. There were fewer adult flies but the population of the rearing tub looked to be the same. There were several large larvae under paper liner in the pupation pail which were transferred to the rearing tub. All of the flesh of the raw potato slices had been eaten leaving just donuts of the peel.

Again no larvae crawled out of the bin in October. The last week has been overcast so the lights have been used a couple of hours daily.

I picked up a sheet of thin clear acrylic which is intended to be screwed down to the top of the bin as a lid to replace the netting bag. Still have to figure out the best way to have venting for fresh air.

2012/11/28 - The population of adult flies has rebounded back to more than 50 and the rearing bin is full of larvae of all sizes. The regular routine now consists of misting the bin before and after having the lights on for a couple of hours daily. The rearing tub is fed every second day with 10 pellets of dog food or a slice of raw potato.

I was given a 26 watt GE 6500K 1600 lumen CFL bulb and substituted it for one of the 23 watt 2700K 1600 lumen 23 watt CFL bulbs used previously. I'm not sure why the GE brand CFL uses 3watts (13%) more power to provide the same output of 1600 lumens. Interestingly the temperature at top of conical light shade is 58C which is 7C higher than observed before with the two 1600 lumen 23 watt CFL bulbs. I have only been using these two 1600 lumen bulbs eliminating the other 900 lumen CFL. This seems to work well as the adult flies are still very active with just these two lights on.

Back on 2012/09/05 the rearing tub was almost full so about 75% of the contents including larvae were put into a second tub which was isolated from the bin so no additional eggs would be laid in the material. On 2012/11/07 after 64 days the last two prepupal larvae were transferred back to the main bin. The material had been kept at 27C.

No larvae have crawled out of the bin for the last 106 days since 20120815. I'm not exactly sure why and I'm reluctant to change anything that might cause the larvae to return to their wandering ways. As such my plans to clean and modify the bin are on hold indefinitely.

2012/12/28 - The BSF population in the bin continues to do well. A typical days maintenance from December is shown below.

Hot water bottles changed morning and evening.
1011hrs Bin:24.3C 73%RH Tub:25.0C Room:21.8C Cover off, fed slice of potato, misted and lights on.
1219hrs Bin:29.9C 45%RH Tub:27.2C Room:21.7C Lights off and misted bin again before putting cover on.
This last update for 2012 is mostly a summary of how my setup evolved over this past year.

At the beginning of January the second generation of larvae were in various stages of development and a few adult flies had emerged (eclosed). Although it's hard to be sure of the exact number, several more generations were produced over the last 12 months. The number of larvae and flies fluctuates but has never dropped to zero so the generations overlap without distinct boundaries.

Different methods and equipment were tried and what has resulted is simpler in most aspects. Details about some are given below:

  • Bin - The bin started out as a pretty sterile environment using new potting soil and small animal bedding. Over the course of the year a layer of discarded puparia and dead flies built up on bin bottom and the flies have defecated or regurgitated on the walls. Other small insects have also set up residence so a more complete ecosystem/environment has developed.

  • Watering & Humidity - Started with a lidded tub with cotton wicks for drinking water and a second screen topped tub for humidity. Both of these have been removed and the bin is just misted a couple of times daily. BSF drink water droplets from the bin walls.

    A transparent plastic cover is kept over the top of the bin which maintains humidity at levels of about 75%. The cover has to be removed to have the lights on and the humidity drops to 45% after a couple of hours with the lights on. Typically the bin is misted just before and after having the lights on.

  • Lighting - Started with Compact Fluorescent Lights rated at a total of 4100 lumens with a color temperature of 2700K. Reduced this to 3200 lumens in November with an equal mix of color temperatures of 2700K and 6500K. Initially the lights were on about three hours daily over the winter through March. This was reduced to two hours daily since lighting resumed in October. There has been no apparent reduction of activity observed with these changes.

    In the summer the bin is moved to a sun lit window and no lights are used.
  • Supplemental Heating - Bottles of hot tap water (link) are used to provide additional warmth but are not used in the hottest months when room temperatures are high.

  • Rearing Tub - The initial tub had a landscape fabric bottom for drainage but the larvae eventually shredded the fabric. Now a simple tub without drainage holes is used and excess moisture managed as required with drier foods such as dog food pellets. Switched to a larger capacity tub tempoarily but found that anaerobic conditions developed in the bottom of the tub. Only smaller tubs are now used.

  • Feeding - Initially about 10 grams was fed to the rearing tub daily but at present only 25% of that amount is fed or about 5 grams every second day. When the rearing tub is nearly full and a portion of the contents is moved into a separate tub, each is fed at this reduced rate.

  • Egg Traps - Initially several egg traps (link) were used and checked daily to see if the BSF were ovipositing (laying eggs). Now that they are reproducing regularly I no longer do the checks but have left one trap in place on top of the rearing tub. BSF have laid eggs in other places within the bin but are probably now only ovipositing close to the food in the rearing tub.

    Egg traps are not necessarily required for ovipositing but are a tool used by researchers to easily count egg clutches in their studies.

  • Larva and Fly Barriers - The netting 'bag' inclosing the entire bin was largely successful in containing any larvae which climbed the walls. Retrieving these wandering larvae from between the outside of the bin and netting became part of the normal routine for a while. While the collar of split foam pipe insulation and the bungee cord securing the netting did not stop larvae from climbing out they do hold the zippered opening in the proper position and keep most of the flies inside the walls of the bin. The zippered opening works well to contain the flies while reaching into the bin to do maintenance.

    The high humidity in the bin caused problems for the strips of conducting tape used for the 'electric fence'. The foil surface delaminated and came off in sections. Also the adhesive backing of the tape lifted from the bin wall in a small area. A better quality tape or even wire might survive better in the humidity. Surprisingly, for reasons not understood, even without the fence no larvae have been climbing the walls since the middle of August.

The bin at the end of 2012 with the netting bag inclosure, water
bottles underneath for heat and two CFLs above for lighting.
The wires are for a temperature probe and for 9VDC power
to the electric 'fence'.

Some Numbers - Temperature and humidity readings were collected daily over most of the year. The number of each type of reading varies because some were added later in the year.

All Temperature, Humidity and Lighting Data

Measurement Readings Average Maximum Minimum Measurement Location
Bin Relative Humidity 1025 69% 92% 24% Inside Bin High On Back Wall
Bin Temperature 1009 24.6C 31.2C 17.4C Inside Bin Low On Back Wall
Rearing Tub Temperature 694 26.4C 32.4C 20.5C Under Castings In Rearing Tub
Room Temperature 255 22.6C 31.3C 20.2C Outside and Just Above Bin
Supplemental Lighting 168 days 2.85Hrs 7.6Hrs 0.37Hrs Daily Lighting Duration

Temperature, Humidity and Lighting Data
2012/06/23 to 2012/12/31

Measurement Readings Average Maximum Minimum Measurement Location
Bin Relative Humidity 277 67.6% 92% 24% Inside Bin High On Back Wall
Bin Temperature 260 25.3C 31.2C 20.2C Inside Bin Low On Back Wall
Rearing Tub Temperature 264 26.2C 32.4C 20.5C Under Castings In Rearing Tub
Room Temperature 254 22.6C 31.3C 20.2C Outside and Just Above Bin
Supplemental Lighting 65 days 2.22Hrs 3.37Hrs 1.27Hrs Daily Lighting Duration

Table Notes:
Regular reording of rearing bin temperature measurments began on 2012/03/06
Regular reording of room temperature measurments began on 2012/06/23
Bin humidity measured with a manual dial type gauge.
Bin and room temperature measured with the remote sensor and base station of a wireless thermometer, respectively. All reading are instantaneous.
Rearing tub temperature measured with a wired temperature probe.
Temperature sensors/probes were shielded from direct sunlight.
The wireless thermometer used for the bin and room temperatures has a minimum/maximum recording feature. Between 2011/11/29 and 2012/11/16 the values recorded were:
Bin Min/Max: 17.1C/33.4C
Room Min/Max: 17.1C/28.9C

Links to information about raising Black Soldier Flies:

'Small Scale Indoor Breeding' topic at the Black Soldier Fly Blog Forum

Cultivation Topics at the Black Soldier Fly Blog Forum

BioSystems Design Blog - A Primer on Black Soldier Fly

BioSystems Design Blog - Black Soldier Fly: Compiled Research On Best Cultivation Practices

Off the Food Grid - BSFL category posts


Raising Black Soldier Flies - Down as of August 2011. See his YouTube channel (link) for videos and for photos of his "Bug Barracks" DIY bin look here or below.

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