Crustaceans are a diverse group, so their life history and ecology offer great variety. Crustaceans are the arthropods that dominate marine habitats, but they are also found in large numbers in freshwater and a few groups have made their way successfully onto on land. When found on land crustaceans are either found in moist protected habitats like under logs or in leaf litter in cool forests, or they are encysted (enclosed in a tough protective capsule, nearly dried out, and dormant).
It is possible to find a group of crustaceans that feeds in just about every way imaginable. There is even a great diversity of parasitic life history strategies used by various crustacean groups. And there's a lot to learn about non-parasitic crustacean feeding, mouthparts, and digestion. As crustaceans feed, they grow, and as they grow they must shed their exoskeleton and produce a larger one; this is called molting. Crustaceans molt as they grow throughout their lives but they molt most frequently during metamorphosis when they are changing from larvae to adults.
(At left, image of Odontadactylus scyllarus with eggs. Image used with permission from Roy Caldwell, U.C. Berkeley.)