Andrea Knapik, age 12, of Stratford, Conn., for her question:
What causes the metamorphosis of insects?
Andy's faithful readers already know that the word metamorphosis means to change form, but the bare meaning does not explain how it works. It merely makes a thoughtful person even more curious, for example, about how a grubby caterpillar becomes a pretty moth.
Many events in the world of nature seem to be accidental. Most offspring resemble their parents,but once in a while a pair of spotted leopards give birth to a jet black leopgrd. A snow white albino may appear in a family of colored kangaroos, field mice, owls, frogs or even fishes. Such oddities of many kinds occur and many of them fail to survive. Nature, however, always tries to make the best of these apparent accidents and some of them lead to stupendous victories.
This natural trend plays a part in the amazing metamorphosis by which a ca~erpi11a=_ changes into a fluttering butterfly. The miracle springs from heredity, a complex process by which parents hand down groups of their own characteristics, along with life, to their offspring. For a long time scientists have known the ratio of inherited traits and also what features an offspring can and cannot expect to inherit from his family tree.
just a few years ago researchers solved this complex process in the miniature world of molecules. The nucleus of a living cell carries a chemical called DNA which is a blueprint of inherited characteristics. The offspring builds itself on this DNA Blueprint. Oddities may be inherited from remote ancestors or they may result from accidents, maybe caused by radioactivity to the DNA blueprint.
The first caterpillar to become a cocoon and then a butterfly may have done so by accident. But it was a happy accident that served a good purpose and nature turned it into a victory over hardship. During the egg and the sleeping pupa stage, an insect needs no food and can survive both cold and drought. By metamorphosis, changing from one form to another and then another, hordes of fragile insects manage to survive from season to season.
The step by step stages by which the changes are made are coded in the dna within an insect's living cells. All its living processes must obey the orders to repeat this blueprint inherited from the family tree. Only a rearrangement of atoms within the dna chemical can change the orders and alter the process of metamorphosis.
The structure of the dna can be changed by extreme heat, radioactivity and other factors. These small changes result in big changes in the offspring. The dna structure responsible for insect metamorphosis may have been set in motion by stray particles from natural radioactivity. The changes in the blueprint would then be handed on from generation to generation.