Welfare Considerations for Farmed Black Soldier Flies (Hermetia illucens)

This post is based on the scientific information within this peer-reviewed academic publication (30 pages; Barrett et al. 2022), but extends beyond simply summarizing the major results of the publication.

Summary

• ~200-300 billion black soldier flies (BSFs) are reared as protein for farmed animal and pet feed across the globe, and the industry is expected to grow. BSFs are anticipated to become the most farmed insect species in the next decade.
• Farmed insect welfare is poorly understood, and animal welfare in the industry is completely unregulated, despite some interest in insect welfare by producers, consumers, and academics.
  • A species-specific review of the empirical literature on BSFs is necessary to identify welfare concerns during the rearing and slaughter of both larvae and adults.
• This peer-reviewed academic publication discusses the many factors that may affect BSF welfare in commercial rearing facilities, including: diseases/parasites, abiotic conditions (temperature, humidity/moisture, larval feed aeration, light, pupation materials, adult spatial needs), nutrition, injury/crowding, handling-associated stress, selective breeding and genetic modification, environmental contaminants, and slaughter methods.
• Some of the most pressing current welfare concerns identified include: starvation of adult BSFs, spatial/environmental conditions inappropriate for the completion of natural behaviors, inhumane larval slaughter methods, and poor-quality larval nutrition (among others). Future areas of concern include pathogens/parasites, genetic modification or selective breeding programs, and the use of low-quality larval feed for large-scale rearing.
  • In addition, the paper provides recommendations for altering conditions that may give rise to pressing BSF welfare concerns, and suggests future research directions that would help assess or improve BSF welfare.
• Ultimately, a welfare investigation should be performed for each species of farmed insect, preferably with input from entomologists and industry specialists (who may lend valuable insight as to how common or important particular welfare concerns are likely to be). These reviews can then be used to develop welfare assessments for insects, and inform welfare policy for the insect farming industry.

Caveats

• For the purposes of this post, it’s assumed there is a non-negligible chance that BSFs are sentient, and thus have welfare concerns.
  • Given the paucity of data on subjective experiences in BSFs, very limited conclusions can be drawn about how farming practices may affect subjective experiences.
• BSF-rearing facilities do not advertise many of their processes, and thus may vary widely in their operating procedures with significant impacts on animal welfare. The areas of concern that are identified in this post may not apply equally across all industry facilities.
• Each insect species is unique; conclusions about BSF welfare will generally not apply to other farmed insects.
• The paper mostly uses population-level survival to draw conclusions about individual welfare (where high mortality across individuals is indicative of low welfare for individuals, though the converse relationship is not necessarily assumed to be true). These are not the same thing, but the paucity of empirical data on (or assessment frameworks for) insect welfare precludes a more fine-grained approach at this time.

Introduction

~200-300 billion individual black soldier flies (BSFs) are estimated to be farmed annually. The insects-as-feed industry is expected to grow significantly, representing trillions of additional farmed-insect lives and deaths within the next ten to fifteen years (de Jong & Nikolik 2021, Rowe 2020). From 2015 to 2020, investments in the insect farming industry increased 30 to 40 fold, from ~10-20 million to over 400 million USD/year. Currently, demand for mass-produced insect protein (to be used primarily as farmed animal/pet feed) is approximately 10,000 metric tons. By 2030, demand is expected to reach up to 500,000 metric tons. Depending on the growth of the aquafeed market, only another 5 years could be needed to scale the industry to over 1 million metric tons (de Jong & Nikolik 2021). The growth of the insects as food and feed industry is global, but many of the largest producers are currently found in Europe, North America, and China–with plans to scale up to multiple production facilities across the globe.

Interest in the insects as food and feed industry is soaring based on industry advocates’ claims that: 1) insects could solve global protein challenges given their highly efficient bioconversion^[1] and high protein contents; 2) some insects (particularly BSFs) could upcycle waste products such as manure into usable protein which, when done locally, could increase the sustainability of protein production; and 3) insect farming could have a lower environmental impact than other kinds of farmed animal rearing (de Jong & Nikolik 2021, Rowe 2020). We do not judge the veracity of these claims in this report as, even if we assume that they are maximally true, the welfare of the insects being farmed should still be investigated.

BSF production

The interest in using insects as food or feed is growing rapidly, and rearing BSFs is attracting most of the attention (van Huis 2020). This is due to their ability to consume many novel materials as feed (that may, if approved for use in the industry, be very inexpensive), low incidence of reported disease, and high nutritional value. BSF larvae (live, dried, or powdered) are the primary product derived from rearing BSFs. Larvae have excellent biomass conversion abilities (Cicková et al. 2015, Lalander et al. 2015) and exchange the waste products they may consume into protein/nutrients that may be consumed by other farmed animals and pets (among other products; de Souza Vilela et al. 2021, Hopkins et al. 2021, Lee et al. 2021).

BSF larvae are reared either in large troughs (of tens to hundreds of thousands of individuals) or, more frequently, in small plastic pans of a few thousand individuals. In large-scale production facilities, pans can be stacked to maximize space efficiency. Each pan of larvae is provided with feed (hereafter, nutritional substrates), which larvae live in and consume to gain mass over 10-20 days of development. BSFs have a highly adapted immune system, enabling them to live in microbially rich substrates (Moretta et al. 2020, Vogel et al. 2018), such as animal manure. However, safety concerns for organisms consuming the final BSF product mean that manure and municipal waste are generally not currently fed to farmed BSFs in Europe and North America (Bessa et al. 2021, EFSA 2015, FAO 2021, AAFCO 2021). For the same reasons, slaughterhouse, meat, or fish waste are currently banned from BSF feed in Europe (Bessa et al. 2021, EFSA 2015, FAO 2021). Instead, the industry currently uses vegetable, dairy, and bakery by-products, spent brewers’ or distillers’ grains, and animal feeds, and in some cases, food waste (such as in China).

Farmed BSF larvae go through six stages (L1-L6), where they continually gain mass, prior to slaughter or pupation; as larvae are generally the final product, the vast majority of BSFs are slaughtered as larvae (Kim et al. 2010, Dortsman et al. 2017). Pupae are only allowed to eclose (become adults) if they are destined to be breeders. Adults are reared at high densities in relatively small mesh mating cages, often with special lights that encourage mating (or in greenhouses). After mating, females will lay 600-700 eggs per clutch in wooden or cardboard ‘eggies,’ usually between days three and six of life (Tomberlin and Sheppard, 2002). Eggs can be collected and hatched onto special, nutritionally rich substrates in the nursery, meant to encourage the survival of young larvae prior to transfer to the pan system (Dortsman et al. 2017).

As the BSF farming industry is relatively new (Rowe, 2020), farming practices vary widely. Producers use different technologies/best practices in their facilities (which may, in part, serve to address population-level variance in the organisms themselves). As one example of this variance, larval slaughter can be as technologically simple as roasting larvae in sand or in pans left out in the sun–or as technologically complex as conveyor-belt-style microwaving machines processing 28+ kg of larvae, or ~150,000 larvae per hour (at 0.18 g each; Chia et al. 2018, Harden & Tomberlin 2016; MAX Industrial Microwaves 2016). Facilities may be entirely run on human labor with little automation (many small-scale facilities in developing nations) or may be highly automated (such as JM Green in China, which processes up to 200 tons of food waste a day with only eight staff; Yang 2017).

BSF welfare in industry conditions

BSF welfare is only relevant if BSFs are actually sentient; however, data on the sentience of insects are unclear and contentious (Adamo 2016, Barron and Klein 2016, Birch 2020, Gibbons et al. 2022) and scientific consensus is unlikely to be reached in the next decade, despite the rapid growth of the insects-as-feed industry during this same time period. My co-authors and I thus employed the precautionary principle: insects may be sentient, therefore, out of an abundance of caution, we should consider their welfare (Birch 2017, Mikhalevich and Powell 2020).

There are no well-established metrics of welfare in insect populations–as such, we used reduced population-level survival (more commonly reported) as an indicator of generally low welfare. Of course, survival can be high and organisms may still be experiencing sublethal, low welfare conditions. However, even if we only consider population-level survival as our indicator, there is still significant room for welfare improvements in the industry. One report, from a BSF facility in Indonesia, suggests that only 70% of larvae survive to pupation, and only 80% of pupae provided the opportunity to eclose will survive to emerge as adults (Dortsman et al. 2017). It is not uncommon for lab studies of BSFs to achieve larval survival of nearly 90% or more, suggesting that better conditions could improve survival (e.g., Dzepe et al. 2021, Miranda et al. 2020). However, this facility may not be indicative of survival (or welfare) in other production facilities.

A review of the literature suggests many welfare concerns exist for farmed BSF larvae and adults, dependent on industry practices (for more on this, view the paper here). These concerns may be the target of interventions to reduce farmed BSF suffering. For the purposes of the review paper, aimed at identifying species-specific welfare concerns for farmed BSFs, Brambell’s (1965) Five Freedoms model of animal welfare was used. This model has been recommended for use in insects by others (Erens et al. 2012), and the concrete nature of the criteria is attractive in situations where welfare data are sparse or unclear. Brambell’s principles include the freedom:

1. From hunger and thirst
2. From discomfort
3. From pain, injury, and disease
4. To express normal behavior
5. From fear and distress

My co-authors and I researched the following variables in order to assess BSF welfare in farmed conditions: diseases/parasites, abiotic conditions (temperature, humidity/moisture, substrate aeration, light, pupation substrates, adult spatial needs), nutrition, injury/crowding, handling-associated stress, selective breeding and genetic modification, environmental contaminants, and slaughter methods. From this review, we put together a list of the most concerning current and future farmed BSF welfare issues and made some recommendations for eventually improving BSF welfare. In addition, we put together a list of empirical research questions which should be addressed to better understand farmed BSF welfare.

Why is this a worthwhile area of research?

BSFs are reared in large numbers globally, with 8-16 billion alive at any given time (~200-300 billion are reared annually; Rowe 2020). While BSFs are not currently the most farmed species of insect, they are predicted to become the most-farmed species within the next few years.

The insects as food and feed industry is expected to grow substantially (30 – 40 fold) in the next 10-15 years (de Jong & Nikolik 2021). Even if only 25% of fishmeal was replaced by insect protein, this represents tens of trillions of additional farmed-insect lives and deaths annually (Rowe 2020). For comparison, only ~79 billion birds and land mammals^[2] are farmed and slaughtered each year for meat globally, though ~31 billion individuals of all those species may be alive at any given time (FAOSTAT, reported in Šimčikas 2020).

There are no regulations that govern how these insects are reared, transported, or slaughtered. Reviewing the biology and behavior of farmed insects in a species-specific manner is necessary to uncover current welfare concerns, make informed recommendations for improving insect welfare, and find critical gaps in our understanding of each species that should be filled by new empirical research.

Findings on current major welfare issues

Tables 2 & 3 of the paper focus on major and minor current concerns my co-authors and I identified for BSF welfare in farmed conditions; we identified nine areas of great concern and three areas of minor concern. Each table also contains recommendations for improving current conditions, or preventing emerging concerns from becoming commonplace in the industry. The scientific justifications for these recommendations can be found in the relevant section of the review (e.g., recommendations about feeding larvae would be supported by data in the ‘larval nutrition’ subsection of the review). We discuss at length four of the nine areas of major current concern below.

Starvation of Adult BSFs and Denial of Foraging Behaviors: A common falsehood repeated about BSFs, including in the scientific literature, is that adult flies do not eat; it is thus standard practice in the industry not to provide adults with any food. The myth that BSF adults do not eat appears to arise from a misinterpretation of a 2002 publication (Tomberlin & Sheppard) which shows BSF females do not need to eat in order to mate and reproduce, and thus continue the colony cycle. Recently, several studies have shown that BSF adults do eat, may have preferences in what food they consume, and that feeding BSF adults dramatically increases their longevity (Bertinetti et al. 2019, Bruno et al. 2019, Fisher and Romano 2020, Macavei et al. 2020, Nakamura et al. 2016, Oonincx et al. 2016). For example, unmated BSF adults fed sugar water can live in excess of 70 days–compared to ~20 days with only water (Nakamura et al. 2016). Current industry practice violates the principle of freedom from hunger, and denies BSFs the opportunity to engage in natural foraging behaviors.

Environmental Concerns in Adult Housing: Adults are housed in mesh mating cages, often at very high densities. This can prevent adults from having the space necessary to complete natural mating behaviors, such as lekking (e.g., large aggregations that females visit to mate, and then leave). In addition, adults often lek near plants in the wild, but plants (artificial or otherwise) are not generally provided in mating cages. While more research is needed to understand if plants in mating cages could restore natural behaviors, the spatial constraints and rearing densities that depress mating behaviors observed in nature could mean that current industry practice violates the principle of freedom to perform natural behaviors.

Inadequate Larval Nutrition: In empirical studies, BSF larvae have been fed everything from human feces to almond hulls and chicken meal (Banks et al. 2013, Lee et al. 2021, Palma et al. 2018). Currently, the industry feeds vegetable, dairy, and bakery by-products, spent brewers’ or distillers’ grains, and animal feeds to BSFs (in Europe and the US), with short-term plans to expand into food surplus/waste (which already occurs in China) and animal by-products. Long-term plans for BSFs propose feeding them manure, municipal waste, and slaughterhouse, meat, or fish waste. Several options for homogenous, low-nutrient substrates (such as brewer’s grain, certain plant wastes, and animal feces) may currently be fed to farmed BSFs, and may reduce survival and welfare to varying degrees in mass-reared larvae. In addition, wood shavings/wheat bran added to the substrate to manage moisture (which, in excess, can drown larvae) can reduce the nutrient content and thus survival. No guidelines exist for adequate nutritional content of larval rearing substrates, which may vary widely based on local substrate availability, cost, or production facility requirements. Current industry practices that use homogenous, low-nutrient-content substrates for rearing larvae will violate the principle of freedom from hunger, by not ensuring access to quality food.

Inhumane Larval Slaughter: Humane slaughter occurs when an animal is either killed instantly (e.g., less than one second) or rendered unconscious until death ensues (for example, via the application of anesthetics). BSF larvae are slaughtered without anesthetic using a variety of methods: boiling/blanching, microwaving, oven heating, sand roasting, roasting in sunshine, liquid nitrogen freezing, air freezing, asphyxiation, and shredding/grinding. Many of these methods take a long time, expose photophobic larvae to light and stressful handling, and could be expected to cause significant pain. In addition, a lack of standardized, welfare-oriented slaughter guidelines in the industry means that even when producers care about improving slaughter welfare, they will not have any resources to assess their own slaughter practices (Bear 2019). If insects are capable of subjective experience, then many of the slaughter methods used for BSFs will violate the principles of discomfort and pain and, potentially, fear and distress.

Other welfare concerns, such as preslaughter larval starvation periods, unlit eclosion cages to delay mating behaviors and oviposition, handling-associated stress for larvae, and abiotic conditions linked to increased larval mortality, are discussed at greater length in the publication. In addition, our report focused mainly (but not exclusively) on mortality-associated welfare concerns. Many conditions that may impact welfare in a sublethal capacity have thus not yet been identified for BSFs.

Findings on potential future welfare issues

Table 4 of the paper focuses on the three major future welfare issues for the BSF industry as it continues to grow: parasites and pathogens, selective breeding and genetic modification, and the use of larval nutritional substrates with low nutritional value.

Parasites & Pathogens: Because of their unique immune system (an adaptation to evolving to feed on microbially-rich substrates like manure; Joosten et al. 2020, Zdybicka-Barabas et al. 2017), BSFs are expected to be more resistant to pathogens compared to many other farmed insects. As of 2015, no large-scale epidemics have been reported by the largest BSF producers in the scientific literature (Eilenberg et al. 2015). However, anecdotal reports of larger disease outbreaks in the industry abound, including viral and fungal infections (reviewed in the paper); these diseases may be associated with significant mortality, as well as suffering related to symptoms that develop before death. Symptoms are pathogen-specific, but some symptoms of common diseases observed in other farmed insect species are: lethargy, sepsis, swollen bodies, feeding cessation and other behavioral changes, and more (Joosten et al. 2020). Disease risks tend to grow as animals are mass-produced in close quarters; it seems very likely that, despite their unique immune system, farmed BSFs will eventually experience significant suffering due to parasites/pathogens.

Selective Breeding/Genetic Modification: Many agricultural organisms are bred for faster development, increased body size, or other behavioral/morphological modifications of value to the agricultural industry. Frequently, these phenotypic changes result in decreased welfare for the organism (e.g., detrimental health impacts of selective breeding in chickens; Paxton et al. 2013). Currently, scientists have successfully modified BSFs in the lab to increase final larval body size by 2-3 fold (via increasing development time) and to create wingless adults that are flightless and can be housed in smaller mating cages (Zhan et al. 2019). These strains have not been used by the BSF industry, but could represent a challenge to welfare in the future. In addition, selective breeding within production facilities to reduce development time, increase body size, change the needed abiotic conditions for successful larval development, or increase reproductive output may result in long-term welfare problems via inbreeding or reduced stress resistance (Gilchrist et al. 2012).

Novel Substrates: Long-term plans for BSFs propose feeding them manure, municipal waste, and slaughterhouse, meat, or fish waste; many of these substrates may be popular for sustainability or cost purposes, but are low in nutrients and very homogenous. Lab studies of many of these substrates have demonstrated that they may pose significant challenges to welfare, even when measured only by population survival. For example, a diet of human feces can reduce survival to as low as 8% (Banks et al. 2013), while 100% meat meal diets reduce survival to as low as 40% for larvae (Gobbi et al. 2013). Larvae do not appear to thrive on animal manure, either, in mass-produced settings: for example, dairy manure reduced survival to 45% (Miranda et al. 2020). Some of these results could also be due to interactions between novel substrates and other abiotic rearing variables such as pH, moisture, etc. that are not yet entirely clear.

It is possible that the industry may not choose to use these substrates, given dramatic reductions in survival that are counter to economic productivity; however, many of these substrates will be particularly inexpensive, and the potential for using insects as waste managers is important for sustainability aims. In addition to reductions in survival, novel substrates may also present sub-lethal welfare concerns.

Novel substrates may also come with other risks–for example, food waste can be contaminated with plastics, glass, and other sharp objects that may injure soft larval bodies if not carefully treated prior to use. Food waste can also be contaminated with soft materials, such as cigarette butts, that may not be removed during pre-processing but contain chemicals not safe for larval consumption–e.g., nicotine, which has proven lethal to other fly larvae (Wolf and Heberlein 2003). Pesticides may also be used to control pest dipteran^[3] populations in agricultural settings, including around food surplus waste or manure, with potentially adverse effects on BSFs if these substrates later find their way to production facilities. In some cases, contamination risks associated with novel substrates could be passed on to final consumers. For example, heavy metals may be found in municipal, household, and vegetable waste (Diener et al. 2015). Bioaccumulation of heavy metals/arsenic can lead to ~50% reductions in survival for BSF larvae at high enough concentrations (Diener et al. 2015, van der Fels-Klerx et al. 2016, Biancarosa et al. 2017, but see Purschke et al. 2017) and may have knock-on effects on farmed animals fed those insects (at unsafe levels, Purkayastha and Sarkar 2021).

A potential near-term future intervention: Extending beyond Barrett et al. (2022)

My co-authors and I identified many current and potential future welfare concerns for BSFs; in most cases, more research will be necessary to identify tractable interventions that will reduce net suffering.

However, advocating against the use of the most clearly inhumane slaughter methods is one intervention that may be worthwhile to consider pursuing relatively soon, when production facilities are being built and slaughter machines that will be used for the next several decades are being purchased. Once production facilities have been built that use equipment that is most likely to be inhumane, it will be much harder to advocate that producers change their slaughter method, due to the economic effects of stopping production and buying new equipment.

At present, blanching/boiling, freezing in liquid nitrogen, and grinding are likely to be the fastest methods by a significant margin, and may even be instantaneous under certain standard operating procedures. By the metric of time-to-death alone, they may be recommended as more humane than microwaving and oven baking. Advocates may consider helping producers develop guidelines that clarify which methods are certainly inhumane, and should not be used. For tractability purposes, advocates may also point to the other advantages of these more humane techniques–for example, blanching leads to excellent microbial decontamination and minimal lipid oxidation, which is good for product quality (Larouche et al. 2019). However, further research is still needed to determine standard operating procedures for each of these methods that will guarantee the quickest, least painful/stressful death for BSF larvae–even when using these more humane methods. In addition, future research is needed to resolve key uncertainties around other non-instantaneous methods like freezing in air and asphyxiation, which may be able to anesthetize insects prior to death (but the amount of pain experienced in the process is still uncertain).

Future research directions

A few additional examples of the kinds of research directions needed, based on our review of the empirical literature on BSFs, are:

Studying Dipteran Pathogens and Parasites: Disease is an emerging area of concern for BSF welfare, despite their highly adapted immune system. Greater funding for scientists to identify wild pathogens that impact BSF populations, and to work with producers experiencing small-scale disease outbreaks to identify pathogens and disease mitigation/treatment plans, would be valuable and, likely, tractable (as scientists have shown interest in studying and managing farmed dipteran disease; Joosten et al. 2020).

Effects of Environmental Conditions on Mating Behavior: Research is needed to assess the impacts of different spatial treatments, rearing densities, and environmental conditions on BSF mating behavior. Spatial treatments might increase mating cage size (decreasing rearing density), or separate male leks from female oviposition sites. Environmental conditions could include artificial or real plants that may encourage both natural foraging and mating behaviors. Without this research in hand, it is challenging to make any concrete recommendations to producers other than ‘larger cages and lower densities,’ which is vague and likely to be unpopular. In addition, BSF natural behavior is poorly understood; only a handful of publications exist that have observed their behavior in natural habitats (especially in their native range). Broadening our understanding of BSF behaviors in the wild will allow more precise guidelines on the enrichments and environments that will benefit them in captivity.

Characterizing Nutritional Substrates for Tests of Larval Welfare: Research is needed to assess the nutritional content of each of the substrates fed to BSFs; at least 50% nutrient content should be maintained in any substrate. Producers may also mix numerous waste streams to increase the heterogeneity of substrates and inoculate substrates with non-digestible material with beneficial microbes to aid digestion. Further research to establish guidelines on adequate nutrition for larval growth, as well as which microbes are most beneficial in which contexts, would aid in guiding policy that standardizes high-welfare feed for BSF larvae.

Welfare Assessment Tools: Following these investigations, welfare assessment guidelines should be developed that could be used to provide welfare regulations for the insect-rearing industry. These guidelines must be informed by species-specific welfare knowledge and should consider the unique challenges associated with insect welfare assessment (e.g., incredibly large number of individuals, reduced reliance on visual/behavioral indicators of welfare, etc.). Industry partners may be valuable in this enterprise–particularly in the early stages of developing guidelines–because of their deep knowledge of the challenges faced by the species in mass-production settings. Mass production may cause rearing variables to have a different effect on insect welfare than in ‘laboratory’ or ‘wild’ settings (Sørensen et al. 2012, Miranda et al. 2020, Scala et al. 2020). While Brambell’s Five Freedoms has been recommended for use in developing insect welfare guidelines (Brambell 1965, Erens et al. 2012), this framework was originally developed for vertebrates and may not be the best philosophical framework for insect welfare. Greater thought should be given to how current animal welfare frameworks may be extended or modified to work better for assessing and researching the welfare of insects.

Conclusion

The insects as food and feed industry already rears ~200-300 billion black soldier flies a year, and the industry is expected to grow substantially in the coming decades. We have demonstrated that there are numerous areas of major current concern for BSF welfare in farmed conditions, including starvation of adult BSFs, environmental concerns in adult housing, inadequate larval nutrition, and inhumane larval slaughter. As the industry continues to scale, there are several areas of emerging concern–including diseases, detrimental physiology or behavioral impacts of genetic modification/selective breeding, and novel but potentially non-nutritious substrates at scale. Significant future research will be needed prior to advocating for any particular interventions, although it may be safe to advocate against the most inhumane slaughter and rearing practices (for example, microwaving or sunbaking larvae to death). Studies that may be particularly important for informing BSF welfare in industrial facilities include studying pathogens and parasites, looking at the effects of adult environmental conditions on mating behaviors, and developing welfare assessment tools specifically for insects. Altogether, this work demonstrates that there is reason to seriously consider the detrimental impacts of farmed conditions on insect welfare and to further research cost-effective interventions for the industry.

Acknowledgements

The information in this post is sourced from a published academic article, which was the product of a prior research collaboration between Rethink Priorities and external academic collaborators; there are also some additional considerations added on the impact of different interventions that are specific to this post.

Bob Fischer, Shaphan Yong Chia, and Jeffery K. Tomberlin all assisted in generating the academic publication; information from this publication was used to generate this post. However, this post was written by Meghan Barrett alone, and is only representative of her opinions. Barrett is currently an NSF postdoctoral fellow: any opinions, findings, conclusions, or recommendations expressed in this manuscript are the author’s, and do not necessarily reflect the views of the NSF. Daniela R. Waldhorn and Elisa Autric contributed to the review and editing of this post.

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Notes

1. ^{^}

    Bioconversion efficiency is (final larval weight - initial larval weight)/Diet x 100%  (Ebeneezar et al. 2021).

2. ^{^}

   This includes numbers for animals that are 1) slaughtered and 2) for meat (so any numbers relating to animals that are transported, or slaughtered but not for meat, are not included). Therefore, for birds, this number includes chickens, but not male chicks or transported live chickens. The calculation also includes ducks, quail, turkeys, and geese and guinea fowl. As for mammals, included here are cattle, sheep, goats, pigs, rabbits, hares, buffalo, horses, rodents farmed for human consumption, and dogs & cats killed for meat. Estimations for each of these categories can be found here.

3. ^{^}

    Of the phylogenetic order Diptera, which includes all true flies, including black soldier flies.