The number of papers exploring the adult behavior/biology of the BSF is extremely limited globally. Predominantly, most work focuses on the the larval development and its uses for waste conversion to protein. This focus is understandable given most industry using this insect for such purposes have made this ability the cornerstone of their operation.

But, as any practitioner (e.g., backyard producer, researcher, or corporation) understands, if an adult BSF colony cannot be maintained and fertile eggs produced at a consistent rate, there will be unpredictability in the system with regards to how much waste can be managed and what to expect with larval output.

I always tell people that have interest this industry that the BSF the colony is the HEARTBEAT of their operation. If it ceases, their larval production also will meet its demise.  Because the colony is so important, I have encouraged researchers to explore the biology of adult BSF. My hopes and ambitions are we can remove the variability with regards to fertile egg production and then focus on optimizing production.  

With everything I have said, a paper was recently published on the adult behavior of the BSF:

Giunti, G., O. Campolo, F. Laudani, and V. Palmeri. 2018. Male courtship behaviour and potential for female mate choice in the black soldier fly Hermetia illucens L. (Diptera: Stratiomyidae).

I am not sure if you can access it- so I will provide a general synopsis: The authors indicate male same-sex mating attempts are made by BSF held in colony. They also indicate wing-beating is a key aspect of the adult behavior with males exhibiting this behavior when attempting to mate with a female. 

Some side notes (outside of the paper) on BSF adult mating behavior:

Always remember that BSF are forced to remain in perpetual lekking (mating) sites. So- why does it matter?

1) Adult males are constantly attempting to mate with females that are, a) not ready to mate, b) already mated and are developing eggs, or c) no longer available as they have laid their eggs.

2) Adult males that have already mated once are most likely still trying to mate with females even though they cannot perform.

3) Adults are not able to regulate their temperature given uniform conditions typically in cages (they only have access to what a producer feels is appropriate). What is best to induce optimal mating, egg fertilization, and oviposition?

4) Cage dimensions are highly variable- more studies are needed outdoors at natural lekking sites. I remember studying such behavior at a poultry farm in Alma, Georgia, USA in 1999. The space and density of flies was quite low when compared to what many producers use. How does forcing a high density impact fertile egg production?

These are just a few thoughts that come to mind with regards to BSF adult biology. But, what this means is currently colony methods are extremely non-biological and thus inefficient. 

If anyone is interested in doing adult behavior work- feel free to reach out to me. I truly believe this aspect of the BSF life cycle is sorely understudied but incredibly important for mass production (a paradox of sorts). Someone could really make a name for themselves by researching this aspect of the BSF.

As always, I like to make sure you all are aware of the productivity of hard-working students throughout the world. This thesis came across my email this past week, and I had a chance to review it this morning (fairly brief- about 30-40 pages of text).

The MS student did a nice job reviewing the nutritional, economic, legal, and marketing challenges associated with the insect-meal industry (for aquaculture in Europe). The obvious points are that insect-meal is still a bit expensive; however, with the industry growing astronomically, the price point (while remaining profitable) should continue. 

If you have time and interest- check out this thesis. Nicely done, Florent!

Introducing Insect-Based Salmon Feed: From a Nutritional, Economic, Legal, and Marketing Perspective. 

Great review article by colleagues and friends (Stefan Dinner and Christian Zurbrügg) assessing the global warming potential when using the BSF to recycle biowaste. 

Mertenat, A., S. Diener, and C. Zurbrügg. 2019. Black soldier fly biowaste treatment – assessment of global warming potential. Waste Management 84: 173-181.

The main take-home message:
1. CO2 emissions from BSF recycling waste is 47X lower than from composting alone.
2. Global warming potential by BSF is primarily attributed to residue post-composting and the electricity needed to run the system.
​3. While there is potential, and no one is denying it, the BSF has more benefits than simply allowing the waste to compost. Using the BSF to recycle waste and then replacing fishmeal with BSF can reduce global warming potential from this industry sector by 30%.  

What can I say? Money in the bank (translation- good news!).

So it has been a few weeks since my last blog post and for that- my apologies. Travel and holidays slowed my reading down and consequently my writing.

The good news is my year is slowing down a bit as I am on my next to last trip for the year and then a brief reprieve with family during the Christmas holiday (lots of time to write during holiday). Other good news is I have a number of papers recently published to review and hopefully share with you as well.

The paper for today's post is pretty cool as it provides a comprehensive assessment of the microbiome associated with different waste streams, facilities, and scales (laboratory and industrial). 

Wynants, E., L. Frooninckx, S. Crauwels, C. Verreth, J. De Smet, C. Sandrock, J. Wohlfahrt, J. Van Schelt, S. Depraetere, B. Lievens, S. Van Miert, J. Claes, and L. Van Campenhout. 2018. Assessing the microbiota of black soldier fly larvae (Hermetia illucens) reared on organic waste streams on four different locations at laboratory and large scale. Microbial Ecology.

Before I review the study and its finding, I would like to spend a few seconds discussing the importance of the microbiome (check out this page as related to the human microbiome). For those that do not fully understand the microbiome, it is the community of microbiomes inhabiting a given environment. This community often is described to include bacteria, fungi, protists, viruses, and more. With the work currently being done, most has focused on bacteria and fungi.  Research is finding the microbiome is extremely important regulating physiology and behaviors of their hosts- something very cool (check out paper on interkingdom communication [in this case, interactions between microbiomes as well as their interactions multicellular organisms).

Characterization of these species is highly dependent on global efforts to describe them all (molecular methods) and store these data in data bases for others to use. Needless to say, even with given technology, we are just scratching the surfaces in terms of identifying and describing the host of microscopic organisms found in practically all habitats around the world. 

Now - back to the study and what they did... and what they found.  

The study explored the microbiome associated with different waste streams from different companies. They determined the microbiome of larvae as well as the remaining wastes after digestion. 

The big picture determined there is tremendous variability across batches within sites as well as across sites. They also determined some pathogens were detected (e.g., Salmonella); however, the origins of these pathogens was not clear. The researchers also determined the microbiome was quite different in the larvae than the substrates on which they feed. This discovery is to be expected as the BSF larvae, like many other saprophytic species cultivate the microbiome associated with a resource as a means to suppress pathogens as well as create an environment appropriate for their maximal use of the resource. 

Takeaway: More work is sorely needed exploring the microbiome for safety and production reasons. 

As a FYI- these authors published another paper on this topic which was reviewed in the blog back in May 2018.

De Smet, J., E. Wynants, P. Cos, and L. Van Campenhout. 2018. Microbial community dynamics during rearing of Black soldier fly larvae (Hermetia illucens) and impact on exploitation potential. Applied Environmental Microbiology 84.

 I will not spend a lot of time going into details on this publication with my colleagues Moritz Gold and Alexander Mathys at ETH in Switzerland, and Stefan Diener, Christian Zurbrügg with EAWAG because the paper is open access (yes!! many thanks, Alex!). I am really excited about the details provided here. And, I think you will enjoy the read as well. 

Gold, M., J. K. Tomberlin, S. Diener, C. Zurbrügg, and A. Mathys. 2018. Decomposition of biowaste macronutrients, microbes, and chemicals in black soldier fly larval treatment: A review. Waste Management 82: 302-318.

One final note- congrats, Moritz on a great paper. Very impressive to witness a PhD student lead such a massive effort to produce such a quality product. Well done!

One thing I always enjoy is reading papers published by graduate students. The paper to be discussed today is by Zhongyi Liu (Jay) and his colleagues out of New Zealand. I had a chance to communicate with Jay a few times over the past year or so. And, I truly appreciate his enthusiasm for working with the BSF.  I am not sure if this is his first paper or not- but congrats, Jay! Job well done. I am glad this paper came across my desk today.

The study is a straight forward life-history study of the BSF when grown on three waste streams. Two wastes are common in such studies (e.g., brewery waste and pig manure), while the third I believe is fairly unique (e.g., semi digested grass). The publication information is:

Liu, Z., M. Minor, P. C. H. Morel, and A. J. Najar-Rodriguez. 2018. Bioconversion of three organic wastes by black soldier fly (Diptera: Stratiomyidae) larvae. Environmental Entomology.

The treatment of most interest to me was the "semi digested grass". This material was not defined in the manuscript (based on my reading- apologies if I missed it) so I am not sure of its composition or how it was produced. I looked up the supplier, and it appears to be a producer of free range lambs. 

The development of BSF was compared across these treatments as well as a the semi digested (e.g., broll- wheat bran and wheat flour).  I have to admit, broll is a new term for me.  Based on information in the study, and new to me, this material is fed to chickens as a feed. This material is the standard for producing BSF used in the primary lab affiliated with this study.

Basic parameters of BSF growth were measured, including survival, development time, larval weight gain, development rate (weight/time), and prepupal dry weight.  There were definitely treatment effects- especially for the semi digested grass (massive amounts of time to develop- 70 d vs 14/17 d on other treatments). Other measures were significantly lower for grass-fed larvae (interesting term use as most recognize its use with livestock production) including prepupal weight being 50-75% less. 

Other factors measured included protein and fat content- this result is interesting as the protein content was comparable across treatments (40-50%), while fat was significantly lower for those reared on the semi digested grass (5% rather than 17% or greater). The fat content in the manure-reared prepupae was low (based on my experiences) at 17%. 

The authors also did a meta-analysis across studies- something I will not dive into here; but, a topic you might consider reviewing to gain perspective across studies.

The authors conclude the semi digested grass is not a suitable resource for producing BSF. However, I would encourage some restraint in closing the door on such opportunities. My reasoning being, 1) it worked (just not to the level produced for other resources), and 2) with what we are learning about the microbiome, I suspect there are steps that can be taken that will allow for enhancements in the system to allow more optimal production levels.

I came across this paper today while surfing the web for new information on the BSF. I have to admit, I hadn't thought about pathogens being associated with seaweed; but, I understand the concern. Especially if someone is considering the mass-production of BSF from such material. In the end, we should all recognize that such assessments need to be made on all potential feed streams for the BSF. Here is the link for the paper, but I am not sure you will be able to access the full publication or not. Just in case, I have provided a summary below.

Swinscoe, I., D. M. Oliver, A. S. Gilburn, B. Lunestad, E.-J. Lock, R. Ørnsrud, and R. S. Quilliam. Seaweed-fed black soldier fly (Hermetia illucens) larvae as feed for salmon aquaculture: assessing the risks of pathogen transfer. Journal of Insects as Food and Feed 0: 1-14.

In this case, seaweed, many types are harvested from the wild or cultivated for use as livestock feed. Based on the introduction of this paper, seaweed can be surface colonized by a variety of human and fish pathogens- namely, E. coli and Listeria spp (examples of fecal indicator organisms [FIO]).

Findings in the study were fairly promising:
1- FIOs were at low levels in the larvae at the time they were harvested from the seaweed.
2-Larval meal and extracted lipids were free of FIOs
3-Handling larval meal and other associated activities resulted in contamination- but processing treatments decontaminated the insect-meal. 

Questions to ponder:
1-What was the microbial load of the BSF used in the experiment at the time of initiation?
2-What is the shelf life of the finished product?
3-Can methods be employed to remove concerns about potential contamination after production (e.g., e-beam technology)? And, if so, is it economical and would it extend shelf life of the product?

I have discussed in previous posts the importance of recognizing, "what you are is what you eat". I think most people recognize this statement for its value as related to another adage garbage in- garbage out. Basically, what you consume impacts your own health and nutrition. 

The same is also highly recognized for diet formulations for livestock, poultry, and aquaculture. Such information is critical for optimal production of a species in confined agricultural settings as well as the economics of the system.

With regards to BSF, we know what is fed to them as larvae impacts their own nutritional value in the end. For example, high carbohydrate diets (e.g., fruits) can result in increased fat content of the larvae. 

A study recently published by colleagues in the UK and Sweden in collaboration with Protix, Inc examined this from a slightly different perspective- specifically, the impact of the stage of the BSF (larva vs prepupa) as well as stage of processing (with or without fat) on the microbiome (the link is related to the microbiome of humans- but it gives a nice overview of the importance of such work) of fish being fed these materials.  Here is a link for a nice review article of microbiomes of marine fish.

The study in question is:

Huyben, D., A. Vidaković, S. W. Hallgren, and M. Langeland. 2018. High-throughput sequencing of gut microbiota in rainbow trout (Oncorhynchus mykiss) fed larval and pre-pupae stages of black soldier fly (Hermetia illucens). Aquaculture.

In the study, they used a control fishmeal diet and various combinations (ration of 70:30) of this diet with either BSF larvae; 1) control, 2) fishmeal with larvae, 3) fishmeal with defatted larvae, and 4) fishmeal with prepupae.

The major findings of the study were:
1- diet impact fish microbiome as it varied in fish across diets
2- data indicate using BSF could enhance some beneficial microbes to fish health

The data produced from this study are a great first step in understanding the trophic (layers) interactions between diet, consumer, and associated microbes. I think there is tremendous opportunity here to unite disciplines (as demonstrated by the diversity of authors on this paper) and figure out the appropriate feed formulations and benefits/restrictions of using such diets.

A couple of questions that come to mind from this study are:
1- What was the microbiome of the insects being used (did any of these microbes proliferate in the fish)?
2- What specifically were the insects fed when being produced for the study?
3-BSF produced by Protix were reared on a different diet than those produced by the researchers. Could this be a confounding factor impacting results (i.e., microbiome)?
4- How does shifting larval diet impact their microbiome and does this translate into impacts of the fish microbiome?
5- I recognize limitations of taxonomic resolution (i.e., clarity of identification and data interpretation), but are there microbes specific to fish that engage in gene transfer with microbes from the insects (i.e., do the microbes merge genetically)
6- Was there an assessment of antibiotic resistant genes in the insects before use and could this impact the fish microbiome?

These are questions resulting from reading the study which could be investigated in the future. I believe the authors laid a wonderful foundation on which to build additional research. 

I had a great visit with colleagues and friends from Malaysia and Italy this past week. All came to learn more about the mass production of the BSF and the science being conducted to optimize the process. 

WK & Thomas, from BETSOL in Malaysia, are currently developing sites for waste management and protein production. 

Francesco and friends from the Instituto Zooprofilattico Sperimentale Lombardia ed Emilia-Romagna were learning about mass production as well as the research being conducted to optimize the process.

What was really nice, besides discussing BSF, was the continued development of the BSF network around the world.

As many of you know, I lead a duel life with one part of career being devoted to research. My laboratory focuses on decomposition ecology as related to a number of topics including the BSF.

​Over the course of the past couple of years I have worked with several of my colleagues (Jibin Zhang and Minmin Cai) on the relationship between antibiotics in wastes and their impact on BSF production. We had a publication come out a little while back that demonstrated BSF and their companion microbes actually degrade the antibiotic tetracycline in waste- which is great news for remediation of associated concerns.

You can learn more about antibiotics in the environment through this Science News and associated scientific review on the topic.

The first paper we published (as previously mentioned) is:

Cai, M., S. Ma, R. Hu, J. K. Tomberlin, C. Yu, Y. Huang, S. Zhan, W. Li, L. Zheng, Z. Yu, and J. Zhang. 2018. Systematic characterization and proposed pathway of tetracycline degradation in solid waste treatment by Hermetia illucens with intestinal microbiota. Environmental Pollution 242: 634-642.

As a followup to this previous work, we just had a second paper published demonstrating the frequency of antibiotic resistant genes (ARGs) in the microbial community remaining in the waste after digestion is reduced.

Cai, M., S. Ma, R. Hu, J. K. Tomberlin, L. S. Thomashow, L. Zheng, W. Li, Z. Yu, and J. Zhang. Rapidly mitigating antibiotic resistant risks in chicken manure by Hermetia illucens bioconversion with intestinal microflora. Environmental Microbiology 0.

More specifically we demonstrated:
1. non-sterile BSF reduced ARGs by 95%.
2. remaining bacteria, which was primarily Firmicutes had a 65% reduction in ARGs.
3. human pathogen populations declined by 70-92%.
4. conditions of the substrate impacted the ability of BSF to have this impact.
5. bacteria associated with BSF most likely play a role in this process (it is not just the BSF).

These data are tremendous as they demonstrate other benefits of using BSF to recycle animal wastes- not just food wastes.