Unknown caterpiller with warning stalks?
Location: Harrisburg, PA.
September 28, 2011 7:26 pm
I was wondering if you had an idea as to what this little fellow is. The first photo shows the results of prodding him with a stem to move him into better camera view. The orange stalks appear to be some sort of defensive measure. Could you inform me as to what they actually do? Any help would be appreciated.
Signature: Joseph Grabko
One of your photos shows this early instar Black Swallowtail Caterpillar on an Italian parsley leaf, one of the garden herbs that serves as a host plant for the caterpillar that is often called a Parsley Worm or Carrot Worm. Fully grown Black Swallowtail Caterpillars have a striking green, black, yellow and white pattern that your individual doesn’t yet possess since it is an earlier instar. Caterpillars molt five times between the time they hatch from eggs until they metamorphose into a chrysalis, and each of the stages is called an instar. The orange stalks you mentioned are a scent organ called an osmetriumthat is characteristic of Swallowtail Caterpillars from around the world. As you indicated, it is a defense measure that will dissuade predators like birds. Your individual is one of the earliest instar images we have received of a Swallowtail Caterpillar displaying its osmetrium.