The caterpillar below is about 1" long. It had eaten its way to the top of a common valerian plant.
This is a caterpillar though not as you know it. It is the larva of a sawfly (Hymenoptera = Bees, Wasps & Ants) that are also called caterpillars.
This species is Macrophya albicincta, that feeds on Valerian and also Elder (Sambucus). The adult looks like this: Macrophya albicincta