Pussy Willow

Question

Large black caterpillars are all over it. What are they likely to become? If nice butterfly, I will let them live; if harmful, they will go.

Answer 1

Not sure what kind but I'd venture to guess that it is the larvae of some type of moth. While the caterpillars may not be considered as bad, they will feed on the leaves of your pussy willow, and with enough of them will eventually defoliate the plant.