To help, to ignore or to eliminate?

Every spring, the eastern US is invaded by a small, furry creature called a tent caterpillar.

The tiny monsters live together in a thick, white mass of silk, crawling forth to strip whatever unlucky tree in which it's built, of every last little leaf. They seem to prefer trees in the rose family, such as cherries, apples and pears.

When they've utterly denuded their host tree, they abandon it, creeping forth across the land in search of something else to eat before becoming adult moths.

Gardeners and lovers of trees hate these things. Children find them adorable.

Already this year, I've ruined my karma by squashing the inhabitants of several such nests that had set up shop in my apple trees. And when those whose nests survived beyond my view begin their migration across my yard, I will tempt karma again, leaving green gooey smears everywhere.

So why is it that away from my yard, working in the city, I feel uneasy about engaging in such murderous behavior? Why do I pass a wayward tent caterpillar wriggling on the hot concrete, far from grass, surely doomed, and argue within myself my ethical options: Walk on by and leave it to slowly die? Hasten the job via shoe leather when the little thing has done my green acres no specific harm? Or carry it to safety in some nearby green area, thus increasing the chances that it will survive and reproduce its pestilent kind?