Many animal life cycles feature specialized life stages

In some groups of animals, newborns look much like miniature versions of the adults (a pattern called direct development). Newborns of most animal species, however, differ dramatically from adults. Many animal species have a life stage called a larva (plural larvae), which is an immature form that the animal takes early in its life before assuming an adult form. Some of the most striking life cycle changes are found among insects such as beetles, flies, moths, butterflies, and bees, which undergo radical change (called complete metamorphosis) between their larval and adult stages (Figure 30.10). In these animals, one stage may be specialized for feeding and the other for reproduction. Adults of many moth species, for example, do not eat. In some animal species, individuals eat during all life cycle stages, but what they eat changes with the stage. For example, butterfly larvae (known as caterpillars) eat leaves and flowers, whereas most adult butterflies eat only nectar. Having different life cycle stages that are specialized for different activities may increase the efficiency with which an animal performs those activities and reduce the competition for food between juveniles and adults.

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Figure 30.10 A Life Cycle with Complete Metamorphosis (A) The larval stage (caterpillar) of the cecropia moth (Hyalophora cecropia) is specialized for feeding. (B) The pupa is the stage during which the transformation to the adult form occurs. (C) The adult moth is specialized for dispersal and reproduction and does not feed.