Metamorphis

Phasmids belong to the insects with imperfect metamorphis. Those insects with perfect metamorphis (eg. butterflies and beetles) have a pupal stage in their developement, between the larve and adult insect. Fully grown butterflies and beetles look nothing like the larval forms. Phasmids on the other hand, look almost the same in the first larval stage as when they are fully grown. Usually the colour is different, and the wings don't appear until after the last skin shed.

Perfect metamorphis:
Butterfly
First the female lays many eggs on a plant which becomes the food source for the young caterpillers when they hatch. After they have eaten their full and grown, each catapiller forms a chrysalis around itself. Some time later, out of the chrysalis emerges a butterfly, the adult form of the insect which looks drastically different from the young larvae.

Inperfect metamorphis:
Leaf insect, stick insect and praying mantis
After the female lays her eggs it takes a few weeks until they are ready to hatch. The newly hatched young (nymphs) are very similar in form to the adults. The larvae then shed their skin approximately six times until they are fully grown. Their appearance does not change much except that they sometimes grow wings or the colour changes.