Welfare considerations for farming black soldier flies, Hermetia illucens (Diptera: Stratiomyidae): a model for the insects as food and feed industry

Abstract

Over two hundred billion black soldier flies (BSF, Hermetia illucens (Diptera: Stratiomyidae)) are reared annually across the globe, with the industry projected to grow substantially in the coming decade. Black soldier flies are being actively explored across the globe for use as livestock feed; fishmeal replacements; biodiesel; human, animal, and food waste management; and even sustainable human protein. Despite the huge number of individual insects reared and interest in BSF welfare by numerous producers and academics, there is no paper that considers the species-specific welfare of BSF in farmed conditions. We review factors that relate to BSF welfare in commercial rearing facilities, including: diseases/parasites, abiotic conditions (temperature, humidity/moisture, substrate aeration, light, pupation substrates, and adult spatial needs), adult and larval nutritional considerations, injury and crowding, handling-associated stress, selective breeding and genetic modification, environmental contaminants, and slaughter methods. We conclude with a discussion of the most pressing welfare concerns for the industry, recommendations for altering the conditions that give rise to them, and suggestions for future research directions that would lend valuable insights to BSF welfare. While this summary is BSF-centric, the core topic of animal welfare applies to all insect models currently, or in the future, produced as food and feed.

Cryptic diversity and signatures of domestication in the Black Soldier Fly (Hermetia illucens)

“…Domestication of H. illucens has also impacted genes associated with behaviour, reproduction, metabolism, immunity, and various regulatory and maintenance genes. Genes associated with brain development ( mbt, SrpRɑ & Ncam2 ) were selected in parallel across the genomes of domesticated H. illucens , indicating an impact on brain function in domesticated populations, most likely at the adult stage (Barrett et al 2022). Genes involved in the development of photoreceptors are also found in parallel across the genome, unsurprising considering light sensitivity has been previously identified as a major determining factor of establishing a successful colony under artificial conditions (Zhang et al 2010; Oonincx et al 2016; Heussler et al 2019; Liu et al 2020; Macavei et al 2020).…”

“…In addition to development, behavioural genes involved in adult male-male aggression may also have been impacted, raising animal welfare concerns if aggressive behaviour is increased (Barrett et al 2022). Changes in behavioural genes may also have an impact on function.…”

No neonates without adults

“…This is certainly bound to be a contentious topic in coming years, as the field of insect cognition has begun to reveal that many insects display more complex sensory processes than previously thought, [ 113–115 ] and will add to the growing conversation concerning insect welfare and welfare‐minded practices. [ 116 ]…”

“…This is certainly bound to be a contentious topic in coming years, as the field of insect cognition has begun to reveal that many insects display more complex sensory processes than previously thought, [113][114][115] and will add to the growing conversation concerning insect welfare and welfare-minded practices. [116] Without diminishing the importance of these achievements, realized or soon-to-be, considerable roadblocks remain. These include the dearth of basic biological research on the adult stage, which in turn affects the ability to understand factors impacting high variability in fertile egg production.…”

Starting with sustainability: utilizing food wastes as nursery feed for black solder fly neonates

“…In BSF industrial rearing process, usually, newly hatched BSF neonates ( rst-instar larvae) are initially reared in on high quality food sources (e.g., commercial chicken feed, wheat bran) instead of 'raw' waste materials [13,14]. This stage is referred as the BSF nursery, which is a compromise to ensure the survival of neonates [15,16], as they are particularly vulnerable in this early stage.…”