He has a new blog post, "Do Bugs Feel Pain?," presenting three lines of evidence that the answer to this question may be "yes."
After this, he says:
So, given that we can’t be sure whether insects experience pain, how should we treat these creatures? When I was teaching insect anatomy and physiology I insisted that the students anesthetized insects before conducting experiments that we would expect to inflict pain on a mouse. My rational[e] is two-fold.
First, it seems ethically obligatory to guard against the possibility that insects feel pain. If we use anesthetic and it turns out that insects don’t experience pain, the material cost of our mistake is very low (a few extra minutes to apply cold or carbon dioxide). However, if we don’t use anesthetic and it turns out that the insects were in agony, then the moral cost of our mistake is quite high.
Second, I think that treating insects as if they can experience pain cultivates an attitude of respect toward living organisms. And this seems like a good thing. We learn the methods of dissection through practices—and we also learn virtues such as compassion through practice. Perhaps we become overly careful in our actions by including animals that aren’t sentient, but world that is more mindful of other beings than is strictly necessary is okay with me.
Of course, there are circumstances in which we are justified in crushing, poisoning, or otherwise harming insects. Nobody wants to suffer hunger or malaria. We must protect our food and bodies. And so inflicting suffering and death is part of life; we live with the existential dilemma that we must kill to live. But we are also obligated to minimize the harm that we do—and insects are a part of this duty.
I agree that killing insects isn't necessarily a bad thing. Indeed, if I were an insect, because my lifespan would be so short, I would prefer to be killed with minimal pain now rather than die by parasites, dehydration, or in a spider's web a few weeks later. (This assumes that life itself would be pleasant, which is dubious.)
However, this killing should be as painless as possible. Jeff endorses euthanasia in the case of laboratory experimentation, but I maintain that it's quantitatively orders of magnitude more important in the case of insecticides on crops. There's a broad spectrum (pardon the pun) of painfulness in the realm of insect-control methods. Some insect-killing practices, like spraying Bt or introducing natural predators, would seem to be very unpleasant. Others, like pheromone disruption or prevention, are nearly free of suffering for the targets, and as a bonus, they reduce insect populations for the future, preventing many lives of suffering before those lives get started.
I hope eventually to do more research and perhaps advocacy in the realm of encouraging farmers to adopt more humane methods of pest control that simultaneously continue to prevent insect lives that aren't worth living. Suggestions from readers on how to begin this are welcome!