A Primer for Insect Sentience and Welfare (as of Sept 2023)

By Meghan Barrett @ 2023-09-26T22:40 (+115)

This post was written by me, Meghan Barrett, in my independent capacity as an academic research scientist and entomologist. None of the organizations with which I'm affiliated should be taken to endorse or support any particular conclusions or resources listed herein based on this post.

Introduction

If you attended my talk at EAG London in May 2023, you may remember this basic narrative: 

Insects might matter morally. There are a lot of them. We can use scientific evidence to make their lives better.

This is the quick case I provide for working on insect welfare. Since that talk, I’ve been encouraged by the amount of interest in the topic among members of the EA community, so many of whom want to learn about insects and their welfare in farmed, wild, and research contexts. The lives and capabilities of our planet’s ~5.5 million species of insects are often surprising and quite poorly understood (even by entomologists!), which can lead us all to make empirically-unsupported assumptions about their sentience, capacity for welfare, and welfare concerns. Although there are many significant unknowns in the science of insect sentience and welfare, it is clear that if we want to help insects, we need to learn what we can about them.

Lots of advocates are doing just that: they’re putting in the work to understand insects’ nervous systems, behavior, and physiology—as well as the scale and contexts of their use and management. I’m heartened to see people take insects seriously. So, as an insect neurobiologist and physiologist by training, I want to do my part to make it easier to learn about these fascinating, diverse, and highly neglected animals.

This post is a quick, non-exhaustive, and lightly-annotated list of resources that can serve as a primer for folks interested in getting up to speed on insect pain, sentience, and welfare as of September 2023. For future readers, it also points toward some places where people can go for the most recent information on insect welfare and sentience. 

I hope this guide is useful for introducing you to the topic – and for demonstrating that there is a lot of rigorous empirical, or otherwise expert, conversation currently happening on the topics of insect sentience and welfare.

Quick caveats

• The welfare-focused work on this list (as compared to the pain and sentience research) is skewed toward the work of Rethink Priorities, my collaborators’ publications, and my own efforts. I’m obviously biased, but I think these folks have done much of the most rigorous work in the space to date. 
• The list is biased towards biological information over, say, economic models or philosophical considerations. I’m a biologist. It’s also probably biased towards neurobiology and physiology over, say, ethology (though I’ve tried hard to include behavioral resources, too).
• The list is intentionally non-exhaustive—it’s a primer, not a research database (if you want that, check out this link here)—so you shouldn’t expect these resources to provide a complete overview of everything you might need to contribute meaningfully to the conversation on insect sentience or welfare.
• This list won’t be updated regularly. It’s the list ‘as of September 2023’. The insect welfare and sentience space is starting to move faster, so this may be seriously out of date within a year or two. 
• Not all work on this list is peer-reviewed (at least in the traditional, academic sense). 
• Inclusion doesn’t equal endorsement. Instead, inclusion on this list is an expression of confidence that either (1) there’s something of value to the work conducted therein or (2) it is an important part of the history and debate of the discipline. 
   

Insect Sentience and Capacity for Welfare

By far the most rigorous and up-to-date work on insect pain/sentience is Gibbons et al. 2022 (Advances in Insect Physiology) which reviews over 350 studies across six orders of insects and two life stages. The paper itself is very long (sections 1 & 2 and 4-6 are most informative to the entomological novice), but you can read a short summary prepared by the majority of the authors on EA Forum here.

Rethink Priorities’ Moral Weight Project has considered insect sentience and capacity for welfare. You can read posts in the series via Bob Fischer (and team)’s work on the forum here (and by reading the forthcoming book, Weighing Animal Welfare, out in 2024). Especially relevant for the insect case are:

• Why Neuron Counts Shouldn’t Be Used as Proxies for Moral Weight by Adam Shriver
• Rethink Priorities’ Welfare Range Estimates by Bob Fischer and team
• If Adult Insects Matter, How Much Do Juveniles Matter? By Bob Fischer and Emily Sandall

Additional Recent Articles of Special Interest:

• Elwood (2023) - Behavioural indicators of pain and suffering in arthropods and might pain bite back?
• Hansen et al. (2022) - Towards machine vision for insect welfare monitoring and behavioural insights.
• Jang et al. (2023) - Drosophila pain sensitization and modulation unveiled by a novel pain model and analgesic drugs. 
• Khuong et al. (2019) - Nerve injury drives a heightened state of vigilance and neuropathic sensitization in Drosophila.
• Perry & Baciadonna (2017) - Studying emotion in invertebrates: What has been done, what can be measured and what they can provide. 
• Strang & Muth (2023) - Judgement bias may be explained by shifts in stimulus response curves.

The History of the Insect Sentience/Pain Discussion:

Beyond the aforementioned Gibbons et al. 2022 review, the following articles are all an important part of the history/debate on insect pain. But readers of this list should be cautioned that not all information contained in these articles is empirically accurate based on the latest scientific evidence. If you’re not familiar with insect neuroscience/behavior/physiology, be cautious trusting any particular conclusion in any of these papers:

• Adamo (2019) - Is it pain if it does not hurt? On the unlikelihood of insect pain. 
  • Please note that direct connections have since been found between the central complex and mushroom bodies of adult fruit flies; Li et al. (2020)
• Adamo (2016) - Do insects feel pain? A question at the intersection of animal behaviour, philosophy and robotics. 
• Barron & Klein (2016) - What insects can tell us about the origins of consciousness.
• Eisemann et al. (1984) - Do insects feel pain? — A biological view. 
  • Despite being one of the most cited articles on insect pain, please note that this article is extremely scientifically out of date. Rethink Priorities has ongoing work to correct the record on this paper’s findings; and see Gibbons & Sarlak (2020), Gibbons et al. (2022b).
• Gelperin (2019) - Recent Trends in Invertebrate Neuroscience. In: Byrne J (ed) The Oxford Handbook of Invertebrate Neuroscience. Oxford University Press, pp 3–30.
• Kakrada & Colombo (2022) - Extending the null hypothesis to invertebrate pain sentience. 
• Key et al. (2021) - Neural design principles for subjective experience: Implications for insects.
• Klein & Barron (2016) - Insects have the capacity for subjective experience. 
  • And see all the response articles linked in the thread at the bottom of the page.
• Mikhalevich & Powell (2020) - Minds without spines: Evolutionarily inclusive animal ethics. 
• Overgaard (2021) - Insect consciousness. 
• Sneddon (2017) - Comparative physiology of nociception and pain. 
• Walters & Williams (2019) - Evolution of mechanisms and behaviour important for pain.
• Wigglesworth (1980) Do insects feel pain? Antenna 4: 8–9.

Insect Welfare Cause Area and Scope

Nearly all of the information on the cause area and scope of the insect issue has come from Rethink Priorities and/or Abraham Rowe; peer-reviewed research on the scale of insect use has not been conducted.

• Although older (2019), this post by Jason Schukraft nicely sums up the invertebrate welfare cause area.
• Lewis Bollard has written about the promise and perils of insect farming here.
• These posts by Abraham Rowe sum up the scale of invertebrate use and welfare issues in the following contexts:
  • Insects as food and feed
  • Silk production
  • Cochineal production
  • Direct human impacts in wild, farmed, and other captive contexts

The General Topic of Insect Welfare:

• Barrett & Fischer (2023) - Challenges in farmed insect welfare: Beyond the question of sentience.
• Crump et al. (2023) - Is it time for insect researchers to consider their subjects’ welfare?
• de Goede D, Erens J, Kapesomenou E, Peters M (2013) - Large scale insect rearing and animal welfare. In: Röcklinsberg H, Sandin P (eds) The Ethics of Consumption. Wageningen Academic Publishers, pp 236–243.
• Drinkwater et al. (2019) - Keeping invertebrate research ethical in a landscape of shifting public opinion. 
• Fischer & Larson (2019) - Collecting insects to conserve them: a call for ethical caution. 
• Freelance (2019) - To regulate or not to regulate? The future of animal ethics in experimental research with insects.
• Klobučar & Fisher (2023) - When do we start caring about insect welfare?
• Lambert et al. (2021) - Wouldn’t hurt a fly? A review of insect cognition and sentience in relation to their use as food and feed. 
• Lockwood (1987) - The moral standing of insects and the ethics of extinction. 
• Lockwood (1988) - Not to harm a fly: Our ethical obligations to insects. 
• Sandall & Fischer (2019) - Be a professional: Attend to the insects.
• Sandhi et al. (2023) - Entomology beyond research and education: 2022 student debates.
• Sebo (2023) - The rebugnant conclusion: Utilitarianism, insects, microbes, and AI systems.
• Smith (1991) - A question of pain in invertebrates. 
• van Huis (2021) - Welfare of farmed insects. 
• Volugari-Kokota et al. (2023) - Insects as mini-livestock: Considering insect welfare in feed production.

Species-Specific Farmed Insect Welfare Concerns:

• This research summary of Barrett et al. (2022) contains the highlights of the peer-reviewed publication on the welfare concerns of farmed black soldier flies.
• This preprint (Barrett et al. 2023a) examines the welfare concerns of farmed yellow mealworms; it is very long and a research summary will be generated by Rethink Priorities after the document is through peer review. I’ll update the post then.
• This forthcoming preprint (Barrett et al. 2023b) examines the welfare concerns of three species of crickets; it is also very long, and a research summary will be generated by Rethink Priorities after the document is through peer review. I’ll update this post with the preprint link soon, and the research summary after peer review.
• This paper by Kortsmit et al. (2022) covers behavioral considerations of farmed house fly and black soldier fly welfare. 
• Aforementioned posts by Abraham Rowe summarize silkworm and cochineal welfare concerns. Jason Schukraft has summarized honey bee welfare concerns (and further reading would include Garrido & Nanetti 2019, and their forthcoming book in 2024 on this topic).
• My forthcoming book chapter on insects in Pain and Suffering in Farmed Animals: First Steps in Better Understanding and Management by Clutton and Musk (2024, Springer) is a primer covering insect biodiversity and cognition, scale of use and management, a quick history of research on pain/sentience, analgesics/anesthetics, conditions that may cause pain/suffering in farmed contexts, and attitudes towards insect pain (by consumers, producers, researchers, the public, etc.). 

Wild Insect Welfare Concerns:

• This research post from Hollis Howe (2019) at Wild Animal Initiative covers humane insecticides.
• This research post from myself and Hannah McKay (2023) at Rethink Priorities covers welfare concerns during wild, invasive spongy moth outbreaks – a demonstration of the scale of this relatively common wild insect problem.
• This research post from Kim Cuddington (2019) at Rethink Priorities covers the idea of whether r-strategist species necessarily have net negative lives. See also Browning & Veit 2021 for another perspective on positive wild animal welfare that may apply to insects in some cases.
• Short article on concerns faced by wild pollinators in policy and research practices – Barrett et al. (2023).

Resources for Continuing Education

• The Insect Welfare Research Society has a monthly newsletter that features the most recent peer-reviewed articles on insect and understudied invertebrate welfare and sentience; anyone can sign up on our listserv here. Please note that I am (as of 2023) the Director of the IWRS.
  • The IWRS also has a research library, which is continually updated to hold all the work published to date on insect pain, sentience, and welfare. There are several hundred articles referenced therein; you can search the library for references that meet your interests here.
  • The IWRS has a virtual research seminar series where academics will share their research on insect and understudied invertebrate sentience and welfare. You can register to attend any seminar, and see past seminar recordings, here.
• Effective Thesis has a post on insect welfare with additional resources here.
• Feel free to follow the work of my lab, which will be opening at Indiana University -Indianapolis in January 2024, as we work on farmed insect welfare and neurobiology.

Books for Understanding Insects:

• Any general entomology textbook will be useful for introducing you to the distinct behaviors, physiology, developmental strategies, and evolutionary history of insects. I think Insects: Evolutionary Success, Unrivaled Diversity, World Domination by Rivers is a friendly introduction for the novice.
• Animal Behavior – Rubenstein and Alcock (2019; read the parts on animal behavior generally, and on insects specifically)
• Ecological and Environmental Physiology of Insects – Harrison et al. (2012)
• Arthropod Brains: Evolution, Functional Elegance, and Historical Significance – Strausfeld (2012)
• Invertebrate Medicine – Lewbart (2011; the parts on insects specifically)
• Insects as Food and Feed: From Production to Consumption – edited by van Huis and Tomberlin (2017)