Not just parsley, lots of plants in the carrot family, these are often poisonous. Most butterflies have a host plants with which they have an affinity. Often times the poisons in the plants are what they are after. They eat the plant, unaffected by the poison, but it will affect many predators who then steer clear!
black swallowtail
https://en.wikipedia.org/wiki/Papilio_polyxenes
Thanks! TIL its caterpillar is often called the “parsleyworm” because the caterpillar feeds on parsley.
Not just parsley, lots of plants in the carrot family, these are often poisonous. Most butterflies have a host plants with which they have an affinity. Often times the poisons in the plants are what they are after. They eat the plant, unaffected by the poison, but it will affect many predators who then steer clear!