No, that is not a Monarch caterpillar on your parsley plant.
July 16, 2011 § 4 Comments
I am often asked “why is that green, yellow, and black Monarch caterpillar eating my parsley”?
Black Swallowtail Caterpillar
Chances are, you will never see a Monarch caterpillar on your parsley. By far and away it is more likely that you have the caterpillar of the gorgeous Black Swallowtail Butterfly (Papilio polyxenes).
Caterpillars that are actively feeding are usually only found on their larval host plant(s), the plant they have developed a distinctive coevolutionary relationship with over millennia. Monarch caterpillars do not eat parsley and Black Swallowtail caterpillars do not eat milkweed, and if either attempted, they would not survive. Black Swallowtails were in the past commonly referred to as the Parsnip Swallowtail as their caterpillar food plants belong to members of the Umbelliferae, or Carrot Family. The diet of the Black Swallowtail caterpillar includes the foliage and flowers of carrot plants, fennel, dill, parsley, Queen Anne’s lace, and parsnips.
Monarch Caterpillars
The Monarch caterpillar is yellow, black, and white. The Black Swallowtail caterpillar is green, black, and yellow.
Metamorphosing from this
to this…
Black Swallowtail Butterfly (Papilio polyxenes)
Beautiful, and very interesting. I never knew caterpillars were so particular about what they ate.
I was washing some parsley sprigs in the sink last week and found a chrysalis hanging from the stem. Thought for sure it was a monarch! Since I’ve found a few caterpillars and more chrysalises on what was left of the parsley plants. I brought them all inside. Two caterpillars are still ravenous but the parsley is all gone! Hoping their instinct will make them form chrysalises since the food is gone!
Dear Jan,
You need to go to the store immediately and purchase parsley or fennel as the caterpillars sound like they are still in the feeding stage. They need to reach maturity to become a chrysalis and will die if they do not have food. Wash the parsley and place the stems in a container with water. Gentyl transfer the caterpillars to the food plant (a soft, smallish watercolor brush is ideal for moving caterpillars).
Thanks Kim! I think we’re doing OK. The last 2 babies are slowing down. They had been stripping the parsley stems and the plant has new foliage which I’m snipping off as soon as I see the leaves! But it seems the 2 are gearing up to morph soon. I’ve raised Great and Black Swallowtails, taking them in when the heat and drought get bad here in FL. I release them near our butterfly weed bushes and have a pan of wet sand to keep them hydrated. Love your site, Kim!