caterpillars on red twig dogwood
This is dogwood sawfly larvae. It will eat a significant amount of foliage, so it can be worthwhile sometimes to take steps to control it, particularly on a small or young plant.
Here is our webpage that includes what they will look like as they mature (actually pretty cool): https://extension.umd.edu/hgic/topics/dogwood-insect-pests-identification-and-management#sawfly
Manual removal is easiest. If you miss a few, it's not a big deal. They show up some years and not others.