If they are sentient and free-willed, I would kill them to protect the innocent. If they are sentient, they are not always evil. Some of them somewhere could be good, or at least not evil. I could see a character of mine killing the larvae, but it would be a source of moral anguish for them.
In one of my settings, there is a race called the Dakary, and insectoid race that is dominated by a theocracy that preaches a religion based on food chain, with them at the top and every other race as food. Their religion is evil. Every member of this race ever encountered by the PCs has been evil. A Dakary baby would not be evil if raised in a different environment. I haven't yet decided whether the PCs will encounter a group of Dakary heretics, targeted by their own church/government for extermination. They have (to this point) always been a threat. That doesn't meant that they are ALWAYS evil, even though there have been no counter examples so far.