Many species of buttery caterpillars must grab with a cremaster when they are pupating or they will fall and die. The cremaster grabs onto the silk pad
they make with silk glands. The spinneret, to lay the silk, is on on thier 'lower lip' or labium. The photographs below are of the hooks at the end of the pupa,
or chrysalis. These hooks must grab into the silk if the caterpillar is a species
which hangs as a chrysalis. The Atala butterfly is an odd one; although it uses a silk girdle, it does not use a cremaster.
Click on any photo to view the enlarged photo.