The picture on the left shows a Black Swallowtail caterpillar getting ready to pupate or form a chrysalis. It has made a silk mat and attached itself at the base. The caterpillar also spun a string of silk around its body and attached the strings to the branch to hold the chrysalis in place in the same way that a telephone linesman uses a leather belt to attach to the pole. Not all butterfly species attach in the same way. Actually, the majority of butterflies will hang upside down from their silk pad.
The pupal shell is developing underneath the caterpillar’s skin. This shell can take many forms and shapes depending on the species of butterfly. Once the caterpillar is firmly in place the exoskelton will split off exposing the pupa. In the case of the Black Swallowtail the final chrysalis will be either green or brown depending on whether the caterpillar is pupating on a green stem or a brown stick. Most butterfly species will stay in the chrysalis for about 1-2 weeks before the butterfly emerges. Several species overwinter as a pupa and will thus enter diapause in the Fall and stay as a pupa until Spring when the butterfly emerges.
Avi Bairagi