Nieky Herr, age 3, of Ephrata, Pa., for his question.

What creature has the shortest life span?

All of us hope and plan far a long and happy life. We eat sensibly and take care crossing streets. With luck and a reasonable amount of care, some of us get to be a hundred years old or more. And the life span of human beings is constantly being lengthened wish new scientific knowledge and up to date medical care. Even so, it stretches to a hundred years or more for only a very few of us.

Some of Nature's creatures are luckier than we are. Some can expect to celebrate a couple of hundred birthdays. While others must crowd all their adult living into a single summer's day. As a rule the larger creatures can expect the longer life spans    the smaller fellows have the shorter lives. This, however, does not always apply. For instance the fair sized carp can expect to live a hundred years or more longer than the monstrous whale and a sturdy turtle can expect to live two hundred years longer than a sizable horse.

Certainly this rule does not apply to individual human beings. A five footer can plan on just as many birthdays as a six footer.

The smallest of all living creatures are the yeasts and bacteria. When times are good and food is plentiful, these minute fellows can enter upon a new life cycle every few hours, or less. However, they do not hatch and die as the more complex creatures do. When time comes to start a new life, one bacterium simply splits into two. In a sense it is without end. For the old bacterium has become two new bacteria without losing its life. So this hardly counts in a record of life spans.

Since the smaller creatures have the shortest of life spans, then we may expect to find the very shortest life cycles among the insects. And this is so. The little day flies crowd all their grown up living into a single summer's afternoon. The May flies    June bugs, Canadian soldiers, shad flies or salmon flies    hatch into adult form only to perish in a few hours. In cities around Lake Erie, where these little fellows are plentiful, bushels of them have been swept up at the end of their single day of activity. However, some of these creatures have been in the egg, larva and pupa state for a year or more.

Counting all stages of development, the little fruit fly may well be the creature with the shortest of life spans. This little creature haunts ripe and rotting fruit. Mama Fruit Fly lays her batch of tiny white egg lets near a food supply. In a short while the eggs have become small white maggots, feeding away on plums and peaches. For a while they rest as scaly brown chrysalises. Then they hatch into full grown flies about one fifth of an inch long. These small, dusky creatures with bright red eyes live dust long enough to lay more eggs for more fruit flies. A11 told, the life span of the fruit fly, from the cradle to the grave, is about two weeks    which may well be the shortest of all life spans.