The views expressed here are my own, not those of the people who provided feedback on the draft.
Summary
- According to the GPT Pain-Track from the Welfare Footprint Project (WFP), “Insecticide-treated nets (ITNs) [link] are not only lethal to mosquitoes but also cause significant suffering before death. When mosquitoes come into contact with the insecticide, their nervous systems are disrupted, leading to intense and prolonged effects. These include uncontrolled movements, convulsions, and muscle spasms, which can last for minutes. This is followed by paralysis and eventual shutdown of their body functions. While effective at reducing disease transmission, ITNs inflict severe pain on mosquitoes during the process, making their impact far from instantaneous or painless”.
- I estimate the ITNs distributed by the Against Malaria Foundation (AMF) in the Democratic Republic of the Congo (DRC) cause 763 times as much harm to mosquitoes as they benefit humans.
- I neglected the effects of ITNs on the number of wild animals because it is super unclear whether they have positive or negative lives. Yet, there is still lots of uncertainty even just in the effects I considered. Just accounting for uncertainty in mosquitoes’ capacity for welfare, I estimate the 5th and 95th percentile harm to mosquitoes caused by ITNs are 0 and 11.5 k times their benefits to humans. So it is unclear to me whether ITNs increase or decrease welfare.
- I believe the large uncertainty about the effects of human welfare interventions on wild (and farmed) animals should push one towards prioritising:
- I estimate people donating to AMF can offset the harm ITNs cause to mosquitoes pretty cheaply, donating 1.19 % as much to SWP as to AMF. This fraction is more robust than it may seem because the harm ITNs cause to mosquitoes is decently proportional to the cost-effectiveness of SWP.
- I would move any marginal donations from helping humans to helping invertebrates, so I would not donate to AMF. Nonetheless, I think directing a small fraction (10 %?) of one’s donations to helping invertebrates would be a good compromise to offset potential negative effects. I encourage people donating to animal welfare to do this too.
Context
I strongly endorse expectational total hedonistic utilitarianism (increasing happiness, and decreasing suffering), and think one can reasonably make comparisons across species based on Rethink Priorities’ (RP’s) median welfare ranges. This post explores potential implications of having these 2 views. I think the takeaways are basically the same under desire theories, as beings want to be happy, and not suffer. However, they may differ significantly if you strongly reject impartiality, or consider RP’s median welfare ranges dramatically overestimate animals’ capacity for welfare.
Harm caused to mosquitoes
Here are my calculations. I describe them below.
According to Open Philanthropy (OP), “GiveWell uses moral weights for child deaths that would be consistent with assuming 51 years of foregone life in the DALY framework [this one] (though that is not how they reach the conclusion)”. I guess 1 mosquito-year of fully healthy life is 1.3 % as good as 1 human-year of fully healthy life, which is RP’s median welfare range of black soldier flies. So I think 3.92 k mosquito-years of fully healthy life are as good as the additional human welfare from saving 1 life under GW’s moral weights.
I guess disabling pain is 10 times as intense as fully healthy life, in which case 2.4 hours (= 24/10) of disabling pain neutralise 1 day of fully healthy life. Consequently, I infer that 392 mosquito-years of disabling pain neutralise the additional human welfare from saving 1 life under GW’s moral weights.
GW’s last grant to AMF, as available on their database on 15 January 2025, was of 41 M$, and targeted DRC, for which GW calculates a cost per distributed net and life saved of 6.78 $ and 5.10 k$. These imply AMF has to distribute 752 nets to save a life in DRC. As a result, 0.522 mosquito-years of disabling pain neutralise the benefits to humans of distributing a net in DRC.
GW calculates that nets in DRC effectively last 1.2 years. As a consequence, 0.435 mosquito-years of disabling pain neutralise the benefits to humans of 1 net-year in DRC.
I guess nets kill 1 mosquito every hour, or 0.0167 mosquitos per net-minute. Accordingly, 26.1 mosquito-minutes of disabling pain per mosquito killed by nets neutralise the benefits to humans of GW’s last grant to AMF.
I estimate mosquitoes’ welfare loss per mosquito killed by nets is equivalent to 19.9 k mosquito-minutes of disabling pain. I got this based on:
3 sets of estimates for the time in the 4 categories of pain defined by WFP for the 4 stages described by their GPT Pain-Track for the impact of ITNs on mosquitoes:
Initial contact. “This stage starts as soon as the mosquito touches the net. The chemicals on the net begin to pass through the mosquito’s outer layer and interfere with its nerves. This leads to quick twitching or slight movements as the nerves start to malfunction”.
Toxic excitation. “In this phase, the mosquito starts moving uncontrollably. It may flap its wings excessively or shake as the chemicals overwhelm its nervous system. This stage is intense and chaotic, as the mosquito's body reacts to the disruption”.
Paralysis onset. “The mosquito’s movements slow down as its muscles stop working properly. It becomes unable to fly or move, eventually becoming still. This phase is marked by a gradual loss of control over its body”.
Pre-mortem decline. “In this final stage, the mosquito becomes completely still as its body shuts down. Its muscles and nerves stop working entirely, and it is on the brink of death. The length of this phase depends on how much chemical it absorbed”.
Aggregating the 3 sets of estimates with the geometric mean, as I guess each component estimate of the time in pain follows a lognormal distribution.
- My guesses that:
- Annoying pain is 1 % (= 0.1/10) as intense as disabling pain.
- Hurtful pain is 10 % (= 1/10) as intense as disabling pain.
- Excruciating pain is 10 k (= 100*10^3/10) times as intense as disabling pain. This leads to roughly 100 % of the welfare loss being caused by excruciating pain. So, if one thinks excruciating pain is, for example, 10 % as intense as I supposed, the welfare loss will be 10 % as large.
I conclude GW’s last grant to AMF of 41 M$ caused 763 times as much harm to mosquitoes via ITNs as it benefited humans. Here are a few ways of the harm caused to mosquitoes via ITNs to be as large as the benefits to humans:
- Excruciating pain 0.131 % (= 1/763) as intense (assuming this only negligibly increases the benefits to humans).
- If so, I would guess excruciating pain to be 131 (= 0.00131*100*10^3) times as intense as a practically maximally happy life.
- As a result, 11.0 min (= 24*60/131) of excruciating pain would neutralise 1 day of a practically maximally happy life. In other words, it would be hedonically neutral to have a practically maximally happy life plus 11.0 min every day of “scalding and severe burning events [in large parts of the body]”, or “dismemberment, or extreme torture”. I would consider this life hedonically very bad.
- Mosquitoes’ capacity for welfare 0.131 % as high (relative to humans).
- RP’s median welfare range of black soldier flies is 3.92 % (= 0.013/0.332) their median welfare range of chickens. So the above update corresponds to 2.05 (= ln(0.00131)/ln(0.0392)) updates relatively as large as going from chickens to black soldier flies.
- Excruciating pain 3.62 % (= 0.00131^(1/2)) as intense, and mosquitoes’ capacity for welfare 3.62 % as high.
- If so, I would guess excruciating pain to be 3.62 k (= 0.0362*100*10^3) times as intense as a practically maximally happy life, and estimate 1 day of this would be neutralised with 23.9 s (= 24*60^2/(3.62*10^3)) of excruciating pain.
- The update on the capacity for welfare corresponds to 1.02 (= ln(0.0362)/ln(0.0392)) updates relatively as large as going from chickens to black soldier flies.
Discussion
It would be great if there were ITNs which painlessly kill mosquitoes, but it looks like there are not any. According to Claude:
- Insecticide-treated nets (ITNs) work through chemicals that affect mosquitoes’ nervous systems, leading to either:
- Rapid knockdown and death
- Repellent effects that deter contact
- All current effective ITN insecticides (pyrethroids, chlorfenapyr, etc.) work by disrupting neural function, which would cause distress to the mosquito's nervous system before death.
- Non-toxic alternatives like physical barriers or natural repellents either:
- Don’t achieve the same efficacy in preventing malaria
- Still cause distress through sensory irritation
I neglected the effects of ITNs on the number of wild animals because it is super unclear whether they have positive or negative lives. Yet, there is still lots of uncertainty even just in the effects I considered. RP’s 5th and 95th percentile welfare ranges of black soldier flies are 0 and 15.1 (= 0.196/0.013) times their median. This suggests that, even ignoring effects on the number of wild animals, and just accounting for uncertainty in mosquitoes’ capacity for welfare, the 5th and 95th percentile harm to mosquitoes caused by ITNs are 0 and 11.5 k (= 15.1*763) times their benefits to humans. So it is unclear to me whether ITNs increase or decrease welfare.
I believe the large uncertainty about the effects of human welfare interventions on wild (and farmed) animals should push one towards prioritising:
- Animal welfare interventions improving the conditions of animals instead of decreasing the number of animals with negative lives, or increasing the number of animals with positive lives. I recommend donating to the Shrimp Welfare Project (SWP), which I estimate has been 64.3 k times as cost-effective as GW’s top charities (neglecting their effects on animals).
- Learning more about helping invertebrates, whose total capacity for welfare vastly exceeds that of vertebrates. I recommend donating to (I ordered the organisations alphabetically):
- The Arthropoda Foundation. Their research priorities are humane slaughter protocols, stocking densities and substrate research, and automated welfare assessment.
- The Wild Animal Initiative (WAI). For instance:
- They intend “to use current and new funding” for, among other activities, “Conducting an analysis of agricultural pest control to better understand the best targets for welfare interventions — first identifying scientific gaps and then developing research plans to help fill them”.
- I estimate paying farmers to use more humane pesticides to decrease the suffering of wild insects is 23.7 k times as cost-effective as GW’s top charities.
No one from the animal welfare organisations I mentioned above reviewed the draft of this post. As always unless stated otherwise, I am speaking for myself.
I strongly endorse maximising expected welfare. Nevertheless, I think donating to the above organisations is even better if one intrinsically cares about minimising the probability of causing harm.
I estimate people donating to AMF can offset the harm ITNs cause to mosquitoes pretty cheaply, donating 1.19 % (= 763/(64.3*10^3)) as much to SWP as to AMF. This fraction is more robust than it may seem because the harm ITNs cause to mosquitoes is decently proportional to the cost-effectiveness of SWP. Under my views:
I would move any marginal donations from helping humans to helping invertebrates, so I would not donate to AMF. Nonetheless, I think directing a small fraction (10 %?) of one’s donations to helping invertebrates would be a good compromise to offset potential negative effects. I encourage people donating to animal welfare to do this too. Decreasing the consumption of animal-based foods, especially beef, has major effects on wild animals, and improving animals’ conditions can indirectly change their consumption too, although arguably much less. On the impact of human diet on animal welfare, Michael St. Jules suggested Matheny (2005), this and these posts from Brian Tomasik, this post from Carl Shulman, and Fischer (2018). There is also the sequence Human impacts on animals created by Michael.
Acknowledgements
Thanks to CB for the comment which motivated me to make this post. Thanks to Abraham Rowe, CB, and Michael St. Jules for feedback on the draft.
If I'm understanding your calculations correctly, the underlying assumption is that the pain you estimate a mosquito to experience for two minutes has the same weight as an entire afternoon of incomparably blissful human existence even taking into account the cognitive differences between a human and a mosquito? There doesn't appear to be an obviously correct way to weight the relative intensity of experience of a human and a mosquito, but this one seems like an outlier; typically arguments for considering insect suffering depend on them being more numerous rather than their individual suffering being orders of magnitude more intense than human enjoyment. In all seriousness, if you do attach such high weights to the possible suffering of individual insects, I highly recommend nontoxic spider repellent, especially around your light fittings as an extremely cost effective intervention.
Some of your more quantifiable estimates also seem selected to be particularly unfavourable to humans. For example, the robustly established fact that humans experience days of pain from malaria infections, (including the vast majority of malaria infections which are nonfatal) is disregarded. Medical literature evaluating anti-malaria interventions often focuses on mortality rather than morbidity too, but it's not weighing up human DALYs against a few minutes of mosquito morbidity! Likewise, the assumption that a typical ITN is killing an average of 24 mosquitos per day seems to depend on an inflated number mosquitos per dwelling, even before the mild repellent effect and low killing efficiency of fleeting contact with the nets is considered.
Thanks, David.
Which 2 min of pain in mosquitoes are you referring to? "I infer that 392 mosquito-years of disabling pain neutralise the additional human welfare from saving 1 life under GW’s moral weights".
I do not kill mosquitoes or other insects inside my house, but I guess quickly crushing insects causes them much less pain than ITNs. "I estimate mosquitoes’ welfare loss per mosquito killed by nets is equivalent to 19.9 k mosquito-minutes of disabling pain".
I kill insects by driving, but I think this is fine. Firstly, the deaths are hopefully pretty quick. Secondly, driving saves me time, and I believe most of my impact comes from my work and donations, not from my direct impact on animals via my diet or driving. I calculate neutralising the harms caused to poultry birds and farmed aquatic animals per person in 2022 only requires donating 0.0214 $ to SWP. I guess my potentially negative direct impact on wild animals can also be neutralised with very little donations.
I used GW's estimate of 5.10 k$ per life saved by AMF in DRC, which is supposed to account for effects on mortality, morbidity, and income. GW's estimate may well not be perfect, but I think the uncertainty is the cost to save a life is negligible in comparison with that of other parameters like the welfare range of mosquitoes.
I wish I had a better estimate, but I did not easily find one. My assumption was somewhat informed by a trip I did to Moshi (Tanzania) in early 2020. There were certainly more than 1 mosquito bitting me per hour during dust, and I was using repellent if I recall correctly. People most affected by malaria may sleep indoors, but have houses with very limited ability to prevent mosquitoes from entering. The roofs can be made of turf too, which would attract mosquitoes.
The 2 minutes corresponds to the estimated 119 seconds of estimated excruciating pain per mosquito death in the aggregate estimate in your spreadsheet, comprising nearly all the estimated utility loss.
It was less about your personal footprint and more about the spiders. I once lived in a place by a river an enormous quantity of insects were attracted by any sort of light bulb, which was where the spiders liked to dine out (unless they were deterred with peppermint spray or their cobwebs repeatedly swept away). A web full of wriggling flies wasn't a particularly attractive sight, but I'm disinclined to believe that web was experiencing utility loss far more significant than anything going on in my life[1] But since you are arguing a few minutes of a single insect ingesting a neurotoxin may be of extremely high negative value, keeping spiders away from insects using cheap peppermint spray seems like an highly net positive form of harm reduction worth considering?
Outdoors at dusk is peak mosquito time though, and 2-3 mosquitos are capable of a lot of bites. I would imagine you had access to some sort of treated nets, and didn't have have to clean 20 or 30 dead mosquitos off the floor every day?
I'd have a particularly hard time believing insects had evolved a complex and intense appreciation of neurological pain whilst far more useful traits like navigation were as simplistic and mechanistic as repeatedly flying into a light source...
Thanks for clarifying. For my guess that excruciating pain is 100 k (= 10*10^3/0.1) times as intense as fully healthy life, the 119 mosquito-seconds of excruciating pain per mosquito killed by ITNs neutralise 138 mosquito-days (= 119/60^2/24*100*10^3) of fully healthy life, or 1.79 human-days (= 138*0.013) of fully healthy life based on RP's median welfare range of black soldier flies.
Got it. I estimate paying farmers to use more humane pesticides to decrease the suffering of wild insects helps 5.74 M insects per $. So, valuing my time at 20 $/h, I would have to save 115 M insects per hour (= 5.74*10^6*20) to be similarly cost-effective. One can support research on more humane pesticides by donating to WAI. They intend “to use current and new funding” for, among other activities, “Conducting an analysis of agricultural pest control to better understand the best targets for welfare interventions — first identifying scientific gaps and then developing research plans to help fill them”.
There were certainly more than 1 different mosquito per hour too. I was indeed outdoors at dusk, which is peak mosquito time, so I used a value corresponding to much less mosquitoes than what I seem to recall. In any case, my takeaways would be the same if the number of mosquitoes killed per net was e.g. 10 % as high. This would correspond to only 2.4 mosquitoes (= 0.1*24) killed per net-day, but still result in AMF causing 76.3 (= 0.1*763) times as much harm to mosquitoes via ITNs as it benefits humans. With large uncertainty, such that it would still be "unclear to me whether ITNs increase or decrease welfare".
Thanks for that clarification. So essentially your claims rest on the utility value of over a day and a half of human life being lower than that of two minutes of a dying insect.
Two comments here:
I'd also point out that even with those pain scales and welfare ranges, the calculation looks completely different if one also factors in potentially intense human pain from [nonfatal] malaria infections multiple times per year and experienced over several days, with [rare] neurological systems which may persist for the rest of a natural human life. Again, I'm not sure exactly what a pain scale for celebral malaria should look like but I'm unconvinced there are reasons for regarding it as so much less intense than mosquito pain it can be disregarded when comparing between species.
I recognise that extremely wide-ranging and asymmetric pain scales are convenient to pure hedonic utilitarians who might otherwise be troubled by philosophical problems like utility monsters or trading off a single torture for a speck of dust in my eye: I just think they're unusual positions not well supported by evidence.
My guess that excruciating pain is 100 k (= 10*10^3/0.1) times as intense as fully healthy life ( 100 k times as intense as the maximally happy instant) implies that 0.864 s (= 24*60^2/(100*10^3)) of excruciating pain in humans neutralises 1 day of fully healthy life in humans. Do you think this is "unconventional and extremely skewed"? Examples of excruciating pain include "scalding and severe burning events [in large parts of the body]", or "dismemberment, or extreme torture". I have not experienced excruciating pain myself, so I would not be surprised if it was 10 % as intense as I assumed, but this would not change my takeaways. I estimate the harms caused to mosquitoes are proportional to the intensity of excruciating pain, so AMF would cause 76.3 (= 0.1*763) times as much harm to mosquitoes as it benefits humans according to the updated mainline numbers.
I am not assuming excruciating pain is 100 k times as intense as the maximally happy instant (as you implied above). This is much more intense than fully healthy life, so I guess excruciating pain is much less than 100 k times as intense as the maximally happy instant.
I assumed the welfare per living time of fully healthy life in a given species is proportional to the welfare range of that species. This does not directly follow from RP's welfare ranges, but does not obviously favour helping animals or humans. My understanding it that RP's median welfare ranges refer to the ratio ("welfare per time of the practically maximally happy animal-year (positive)" - "welfare per time of the practically maximally sad animal-year (negative)")/("welfare per time of the practically maximally happy human-year" - "welfare per time of the practically maximally sad human-year").
Yes. I can't think of any pain in which I would prefer to die than suffer for 0.864 seconds per day, particularly not if the remaining aspects of my life were "practically maximally happy".[1]
I find it even harder to imagine that an insect can distinguish between painful sensations to the degree that a pain scale with at least 100k points on it would be appropriate to approximate their welfare on,[2] still less that an appropriate use of such a scale is to multiply a human/insect welfare ratio to conclude that the complete cessation of function of that simple insect nervous system is a few orders of magnitude more intense conscious experience than the "practically maximally happy" (or even average) utility of a human.
If I did think [potential] sub second pain was as significant as an entire day's welfare, I would probably not endorse electrical stunning...
I mean, they've only got 200k neurons to divide between all their functions. (This isn't an argument for neuron count being a good proxy for moral weights overall, merely an observation of how extreme the pain scale looks in the context of how simple the insect's system for parsing stimuli appears to be)