There once was a boy, the story goes, who lived in a dingy New York City high-rise apartment, where he learned little about trees and grass and the bugs that live in them. One morning he looked through his bedroom window, and peering up at him from the windowsill was a long, green praying mantis.

"Mommy!" he exclaimed. "The Martians have landed!"

Another boy of my immediate acquaintance, now almost grown, once was impressed -- as many are -- with the apparent ferocity of the praying mantis, which he pronounced "brain menace." This endeared me to the mantis even more.

So it is with heavy heart I confess that I have interfered with the life of one of these small creatures whose only aim in life is to rid us of other bugs.

A plastic lawn bag half-filled with grass had been resting on the patio awaiting disposition. When I lifted it to put in more clippings, there at its opening was the biggest, greenest praying mantis I had ever seen. I gave the bag a nudge and the mantis sprang onto the ground. It rested there, as they do.

That is one of the most appealing things about mantids: their trust. You put them someplace, they stay. Hours after you have spotted one "hiding" on a Japanese holly or euonymus, it is still there waiting--cunning front legs up in the attitude of prayer -- for another insect to fly by. Mantis, in ancient Greece, meant "diviner," prophet or soothsayer. In a way, the term praying mantis is redundant.

This happens to be an especially fine time of year for mantis-watching. According to Kay Weisberg, zookeeper at the Smithsonian's Insect Zoo, the adults are out mating and laying eggs. When they get hungry, they eat flies, cockroaches and crickets. (One of the larger mantids has even been known to eat a mouse.) These are some of its charms.

That the female is often known to bite the male's head off at the peak of mating is one of its lesser charms. But it does enhance fertilization by severing a nerve in the male that inhibits copulation. "To the female mantis," says Weisberg, "the male is just food." If mating mantids are disturbed, or if the female sees the male as he creeps slowly toward her (sometimes at the rate of a foot an hour), it's all over.

The egg cases (called ootheca), in which mantids spend the winter before hatching in the spring, look like little sponges and may be found on bushes.

Not knowing it is an egg case, people will bring one in the house. "They think it's neat," says Weisberg, who is often called "Bug Lady" by coworkers passing her in the hall. "They put it near the window and the warmth of bringing it in the house will trick the mantids. Suddenly there are hundreds of little mantids on the windowsill."

The Insect Zoo also sometimes raises mantids. "Lots of times when they come out we just kind of let them eat each other. Many die. Then we separate them, feed them baby fruitflies, then houseflies, then baby crickets." The rule of thumb is to feed it something smaller than it is.

"What we try to encourage," says Weisberg, "is for people to find them, collect them, bring them in and observe them for a day or two and let them go." At this time of year, of course, one might be interrupting the reproductive cycle.

I opted to leave the mantis I found outside.

As the big green mantis continued to rest there on the lawn, I went about the business of overseeding a sunny area with Kentucky 31 tall fescue. Finding a large clump of dead grass, I naturally went for the lawn bag. And stepped on the mantis.

I didn't realize what had happened until it crawled away; looking mortally wounded. What had I done?

It sought refuge under a yew: going away to die, no doubt. The mantis was mourned the rest of Sunday afternoon; family members offered sympathy in varying proportions.

The next morning, I was up with the October dawn. There was a murmur in the air. I went downstairs and looked out a porch window to discover the source. Grackles filled the sky and the neighbor's oak tree. I noticed a praying mantis clinging to a porch screen under an opened jalousie, where, perhaps, it was safe from birds. Here's a bug as wise as it looks.

But its appearance on closer examination! Past the intelligent eyes, it was haggard, out of alignment, brownish and turning black toward the end of its abdomen . . . where someone had stepped on it.

It appeared to be hanging on for dear life; I wallowed in guilt.

I considered catching bugs to feed it, recalling the time I shocked a young boy by killing a fly to offer to a potential mantis pet. I had also tried to interest the subject in raw hamburger, but abandoned the idea of domesticating a mantis when it showed no more interest in meat than a Venus Fly Trap did in another failed experiment.

I halfheartedly killed a spider, and botched the job. This praying mantis was just going to have to prey for himself.

I thought to call it Rocky, having observed its personality -- its tenaciousness -- in clinging to the porch screen. It spent four days in the same place.

At the end of the four days, it had miraculously turned green again. But was it still Rocky?

The next day it was gone.