Laurie Kohout, age 11, of St. Paul, Minn., for her question:
CAN A CATERPILLAR REALLY BECOME A BUTTERFLY?
Naturally we know that six mice and a pumpkin cannot turn into a splendid coach and horses. This pretty fairy story is downright impossible. Surely then, it must be downright impossible for a wormy caterpillar to turn into a beauteous butterfly with wings like flowery petals. Ah, but this is another story a real story of one of nature's miracles.
The world of insects is full of astounding surprises, but the most unbelievable event occurs in the life of a grubby caterpillar. Biologists have a special name for this impossible miracle. They call it complete metamorphosis, which in plain language means a complete remodeling job.
The life cycle of a butterfly evolves through four very different stages at least on the outside. It starts as an egg, with a busy inside story, as cells divide and multiply. Directed by certain hormone secretions, they arrange themselves around key centers that carry inherited blueprint patterns.
Eventually the egg hatches into a grubby caterpillar, all set to devour enough food to last the rest of his life. He munches, molts and finally grows big enough for his next phase. This requires a very quiet period, for some undisturbed concentration.
At this point, the average butterfly caterpillar enfolds himself in a crisp, weatherproof chrysalis, usually suspended from under a matching leaf. He seems to be sleeping. But all is not peace and quiet within, where the most fantastic remodeling job in the entire world of nature is going on.
Inside the quiet chrysalis, the cells of the caterpillar body break apart and form a soupy mishmash of biochemical ingredients. Surely any reorganization is impossible. Not at all. The egg cells that produced hormones and the blueprint centers still are active. Now they order the construction of other cells and arrange them to build key parts of a very different body.
When this miraculous metamorphosis is completed, the same insect has a very different looking body. The chrysalis cracks open and a winged adult butterfly emerges to dry his wings in the sunny air.
In most species the adult butterfly lives only a couple of weeks or so and may eat nothing at all. The only thing on his mind is to mate so that eggs may be produced for the next generation. Certainly he cannot hope to cope with a chilly winter. However, the eggs or maybe the tough pupa can survive until next summer. Complete metamorphosis made it possible for the butterfly clan to survive through the ages.