It has always seemed unproblematic to me to kill grubs and spiders, so long as no species were eliminated. I just realized why. It’s because they’re r-selected.

The purpose of a K-selected organism is to survive to adulthood. That’s why there’s negative moral weight to killing humans or dogs. By contrast, an r-selected organism fully expects that most of its offspring will die before reaching adulthood. Grubs are designed such that most of them die. Beetles don’t mind this. Your empathy exists to protect another human’s investment of resources into their child. Beetles and spiders have no empathy because they make minimal investments into their offspring.