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) 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 GiveWell’s (GW’s) last grant to Against Malaria Foundation (AMF) of 41 M$ caused 763 times as much harm to mosquitoes via insecticide-treated nets (ITNs) as it benefited 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:
  • Animal welfare interventions improving the conditions of animals instead of changing the number of animals. 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. I recommend donating to the Arthropoda Foundation and Wild Animal Initiative (WAI).
• 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^[1]. 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 of 41 M$ targeted the Democratic Republic of the Congo (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^[2], 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^[3]:

  • 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^[4].

• 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^[5]. Under my views:

• Both are practically proportional to the intensity of excruciating pain^[6], so uncertainty in this has a negligible effect on the fraction.

• Mosquitoes’ capacity for welfare is decently proportional to that of shrimp, as RP’s median welfare ranges of black soldier flies and shrimp were determined with the same methodology.

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^[7].

1. ^{^}

    Mosquitoes belong to the order Diptera, and black soldier flies are the only species analysed by RP of that order. I asked Bob Fischer, who led RP’s moral weight project, about a best guess for the median welfare range of mosquitoes that RP would have obtained if they had analysed them. I privately disclaimed I would publish this post without Bob’s guess, but Bob did not share one.

2. ^{^}

    I did not easily find estimates.

3. ^{^}

    The quotes describing the 4 stages are from the chat where I got the 1st set of estimates.

4. ^{^}

    Aggregating with the continuous version of the geometric mean of odds lognormal distributions whose logarithms have the same standard deviation results in a distribution whose mean is equal to the geometric mean of the means of the lognormal distributions.

5. ^{^}

    If they were proportional, the fraction would be constant regardless of their uncertainty.

6. ^{^}

    The past cost-effectiveness of SWP becomes 10.0 % (= 64.1/639) as large if excruciating pain becomes 10 % as intense. Likewise, the harm to mosquitoes becomes 10.0 % (= 76.5/763) as large if excruciating pain becomes 10 % as intense.

7. ^{^}

    I ordered the names alphabetically.