Larvae are the distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. In this book, the authors present current research in the study of the morphology, biology and life cycle of larvae. Topics include the morphological changes of marine fish larvae and their nutrition needs; spawning and nursery areas of neotropical fish species; larvae and embryonization principles of ontogeny in arthropods; larvicidal lectins and trypsin inhibitors isolated from different plant tissues; aquaculture production and larval rearing; expression of recombinant proteins in insect larvae; and adaptive plasticity and evolution in larvae with particular reference to the chironomid midge.