A pupa is a metamorphis stage that a hemimetabolous insect--such as butterflies, beetles, wasps and bees--must go through before reaching the adult stage of its life. During this time the insect goes through a radical transformation and the creature does not eat during the process. Pupa tend to hang from branches of a tree or in an area that is not often disturbed, such as on the outside of a house near the attic or a part of the roof. The pupa stage can last from a few days to several months.
Notice a silk padding or covering. Butterfly pupa hang from a silk padding from tree branches. Moths hang in a silk, cocoon-type covering.
Look at the color of the pupa. Most start out white then turn brown, while others are green. For example, butterflies have a green pupa, but beetles have white and brown pupa.
Examine the shape of the pupa. They are oval-shaped and have a structure that starts small on one end and grows in size at the other side. The side that is smallest is where it hangs.
Look to see if there are ants nearby or adults of the same insect. Butterflies tend to be protected by ants during the pupa stage, while other insects will be protected by adults of the same insect.
Notice if there is a shell covering. Few insects such as moths use a shell to cover themselves throughout the pupa stage. The shell will eventually break open for the insect to live out its adult life.