Once every seventeen years, on a warm night in May, an invading host, waiting underground, rises at countless spots between the Atlantic Ocean and the Mississippi River.

Emerging from their hiding places, the invaders spread out to take possession of forest, wood land and orchard. They wear uniforms of black with orange trim, and shining cloaks decorated with the letter ."

Who are these strange creatures with gleaming red eyes? Invaders from Mars?

Not at all; they are the periodical cicadas, better known as the seventeen-year locust. Actually they were not locusts, but insects of a different order.

Later on we will tell you how they were first mistaken for locusts.

Seventeen years earlier, in July and August, these insects began life as tiny antlike creatures, called nymphs, coming out of nests in twigs of trees and brushes. After scampering briefly on bark and leaves, they dropped on earth, where they quickly burrowed into the soil, to be seen no more for seventeen years.

Below the surface, a foot or more, they hollowed out tiny clay cells. They sank their beaks into tender roots for juicy nourishment, and settled down in their dark tombs for almost their entire lives. They seldom moved except to shed their clothes and enlarge their chambers as they increased in size.

As the seventeenth winter of under ground darkness drew to a close, these earth-dwellers sensed that an important change was due, and they stirred into action. During late winter and early spring they gradually tunneled upward until they touched the surface. There, they waited for nature's mysterious call that would send them aloft by the millions, for a brief and noisy life in the sunshine.

Strangely enough, though they had been isolated from one another in solitary confinement for almost seventeen years, they now respond simultaneously to the same inner drive to begin their final cycle of courtship, to carry out the Creator's command: "Be fruitful and multiply!"

They have only several weeks of sunshine in which to carry it out; then they die. Their offspring, emerging from millions of tiny eggs, will repeat exactly the same cycles as their parents: going underground immediately after birth, living in solitary confinement for seventeen years, then suddenly emerging all at once in the course of several nights and transforming overnight from creeping insects into winged adults, to mate and lay eggs for a new generation of 17 year cicadas before they die.

Until recent years, no one ever saw the emergence and transformation of the periodical cicadas, since this was done under cover of darkness, and unexpectedly.

In recent years, however, observers armed with powerful lights and cameras, and with considerable patience, have watched and recorded the amazing transformation.

Here is how they describe it: No sooner does the cicada nymph - somewhat resembling a brownish colored little lobster, with oversized front claws and blood-red eyes - scramble out of the earth, it heads for the nearest tree or post.

Climbing part way up, it anchors its claws into bark or leaf. Now it arches its back, twisting and shaking. Suddenly a split shoots up the back of its shell. As the convulsions continue and the split widens, a creamy-white creature slowly pulls itself free, leaving the empty shell clinging to whatever it had been anchored in.

Red eyes and black shoulder patches stand out against the white.

Curved claws, no longer needed for digging, have given way to slender forelegs. This is the adult cicada. In this stage the cicada is completely defenseless. Its outer skeleton is soft and flabby; its wings have no power to fly. But this condition changes overnight.

The crumpled wings expand into a three-inch spread ready for flight. As the outer shell hardens, creamy white turns to gray or brown, then to glossy brownish black.

Orange re-adorns the margins and veins of the wings, while a dark " W " shows up near each wing tip. By morning a new bumblebee-size insect flies high in the treetops.

Few sights are more impressive than a moonlit wood filled with transforming cicadas!

After enjoying the warm sunshine for a week or ten days, the cicadas get down to the serious business of finding their mates.

Within a few days the female begins to lay eggs beneath the soft bark of twigs of plants-stems.

The Creator has provided the female cicada with a sawtooth chisel - a horny stiletto with two sawtooth ends - along her egglayer on the lower abdomen. Using these sawtooth blades the female cicada carves rows of twin slits. Into each of these pockets she pumps a dozen or so eggs. Before she dies exhausted, she may deposit as many as 600 eggs.

In July and August, a few weeks after the sound of the whirring and buzzing of male cicadas (female cicadas are silent) has been stilled and the last egg has been laid, millions of tiny creatures will hatch from the eggs, and start a new brood of "17-year locusts."

How the Cicada Was Mistaken For a Locust

American Indians knew the cicadas; they roasted and ate them, although their sudden appearance mystified them.

Cape Cod pilgrims, however, were terrified by the emergence of vast and noisy swarms of these insects in 1634. They concluded that these must be locusts, the ancient plague of Egypt.

Their illusion was confirmed by the fact that the insect seemed to call, " Pha-a-a-a-a-a-raoh!"

Actually locusts and cicadas have little in common, though some people may think they look alike.

The locust is a migratory grasshopper. He has strong jaws which can strip vegetation to the roots, and he is well known for his incalculable damage in the Middle East and Africa. He often migrates in vast swarms for hundreds of miles.

Cicadas are sucking insects which live on sap from trees and shrubs; their mouths are not made for chewing. Cicadas do not migrate and each dies within a few hundred yards of his burrow.

Cicadas apparently inflict little damage by their long years of sap sucking, either as burrowing nymphs or as winged adults. They may cause some damage to young trees and shrubs by slashing of branches during egglaying.

Healthy woodland suffers no hurt beyond the loss of some weak twigs. Cicadas never attack fruit, flowers, gardens, or farm crops. Nor are they capable of stinging.

But man can do, and often does, a lot of damage to cicadas. Wherever he cuts down trees and builds roads through cicadaland, he destroys their homes. It would be a shame if this unique and fascinating creature were gone forever.