Pupa, Chrysalis or Cocoon?

Invertebrates go through two types of growth stages. One is called incomplete metamorphosis. This is when the invertebrate undergoes little, or no difference, as it matures into an adult. Grasshoppers are a good example. The young (nymphs) look identical to the adults except at the very last exoskeleton moult (instar). They then develop a usable set of wings. Some stick insect species never experience any change other than size as they mature, but a few do produce wings (sometimes these are only vestigial ). Then we have my favourite, complete metamorphosis. This is the really amazing one! The embryo becomes a larva then pupates into the adult (imago). The pupa is where all the body change is going on and I like to think of it as a mould, as it usually shows all the features of the adult yet to emerge. In the Lepidoptera order (butterflies and moths), the pupa is referred to as a chrysalis. The duration inside the pupa depends on the species and the climate. The cocoon is the casing around the pupa that some, but not all, species choose to make. Some beetle species make a cocoon out of the substrate around themselves. Some moth species spin the most incredible silk cocoons. Whatever they look like, the cocoons are simply made to help protect and camouflage the pupa. Just fantastic!

Chinese Owl Moth caterpillar just starting pupation. The external skin will harden and become black in colour. There is no cocoon as it all takes place hidden underground.