Do caterpillars have free will? What free choices resulted in them being paralyzed and eaten alive by wasps?
In its current life it may not have the intelligence to act morally. But once( before it became a caterpillar ) it had a body of moral sentiment being with power of discrimination. It made bad choices at that time and thus induced suffering in current life.
Why is there any more or less moral weight to the wasps lifecycle than any other predator along the food chain?