I almost lost it right then. I would have screamed if I'd had a voice any longer. But I was already half spider. And I was staring at Ax as he underwent a change very similar to my own.

I was watching him with vision that was half human and half the shattered, broken-mirror vision of the spider's compound eyes.

Something horrifying was growing from the place on Ax's face where a mouth should have been. Something huge and bulging and foul. Two monstrous, swollen things like . . . like nothing I'd ever seen before. They were jaws, but huge and outsized. From the end of each one, a wicked, curved fang grew.

Sometimes you really, really need eyelids. There are definitely some things you don't want to have to see.

I knew the same thing was happening to me. My bulging jaw parts grew till they entered my own distorted field of vision.

Fortunately, I didn't have to worry too long about the jaws. See, I became distracted when legs suddenly exploded from my chest.

SPROOOT! Four new legs, two on each side, just shot out of me, like I was a tube of toothpaste someone had stomped. They sprouted all Gumby-unformed, then began to form joints. Way too many joints.

My human legs and arms were changing to match these first spider legs. I fell forward, no longer able to stand erect.

It wasn't much of a fall. I was already pretty small. The pine needles beneath me already seemed to be as big around as a human finger.

Not that I had any fingers left to compare with.

All the while, new eyes kept opening suddenly where eyes absolutely did not belong. Some were compound eyes. Some weren't.

Then, as if the extra legs, and the mix "n"

match eyes, and the huge jaw-and-fang combo weren't enough, some new leglike things came sprouting out of my ... well, out of where my neck used to be. They were like extra legs, only they weren't. I had no idea what they were. But they moved. Much later, I found out they're called pedipalps.

A sort of cross between a mouth part and a leg.

My head was swelling, compared to the rest of my body. It was gigantic ... in a small way. My entire body was now divided into two big chunks: a sort of bulging head and an even bulgier body.

I was almost entirely spider now. The pine needles that had seemed as big as fingers were now as big as two-by-fours.

As the last touch, strangely soft hairs began to grow from everywhere on my body.

It was the hair that seemed to trigger the awakening of the spider brain.

The wolf spider has good eyes for a spider. But it's all the thousands of tiny hairs that really get the spider brain's attention. They sense every subtle clue in the wind. Every minor movement in every direction.

And all of a sudden it felt like the whole world was moving: leaves, pine needles, the dirt beneath my claw-tipped eight legs, bugs in the dirt, moles under the ground, birds in the air.

All of it seemed to be hardwired into the hairs that covered my spider body.

With all that sensory overload, the spider brain woke up. I had been afraid it would be like the brain of an ant: a mindless machine. Or that it would be the terrified, fearful, panic-stricken mind of a prey animal.

But oh, no. Definitely no.

They didn't call it a wolf spider for nothing.

This guy was tiny, no more than two inches from the end of one outstretched leg to the end of the farthest back leg. A toddler could easily crush him underfoot.

But I guess it isn't size alone that makes a predator, because as soon as I felt the edge of that spider brain I knew this boy was trouble.

The wolf spider was a killer.

Hunger.

That was pretty much what the spider mind had to say: hunger, it was hungry. It wanted to hunt.

It wanted to kill. It wanted to eat up a few nice juicy bugs. It was hungry.

Did I mention hunger? And it didn't care what kind of bug. Could be beetles, could be grasshoppers, could be crickets, could be a big mean mantis. The spider didn't care. It ruled the world of bugs.

It was to bugs what a lion is to a herd of antelopes. It was a shark among guppies.

They could run from the wolf spider, but they couldn't hide.

Motion! Something moved, left to right across my field of vision, and I was after it like a dog af ter a rabbit.

Eight legs powered up and I blew across the forest floor like a drag racer firing out of the start ing gate.

The world was weird to my eight spider eyes. I saw colors no human ever saw. It was like when you mess with the color and tint knobs on the TV.

Things that should have been brown were blue, and green was red, or whatever. From some an gles the pictures were almost clear, but a second later everything would shatter into bits and I'd be watching a million tiny monitors at once.

I never could make logical sense out of it.

But mostly what I saw was movement. I was very, very interested in movement. My eyes and every hair on my disgusting little body were about spotting movement.

And when the right thing moved, my body just answered all on its own.

It was a rush, as they used to say in my dad's day. A charge. It was like tapping into the main pipe of adrenaline. It was electric. It was nuclear.

I blew across pine needles and fallen leaves and over patches of dirt and I kept that moving bug in my field of vision and I knew what I was doing, I mean, I knew I was Marco, a human in morph, and I knew I didn't really want to eat that racing bug, but man, I was too jazzed to stop.

The prey was running and I was the predator. I had evolved for hundreds of millions of years to do exactly this. When Tyrannosaurus rex was still millions of years away from even thinking about evolving, tiny arachnid hunters were killing and eating. The entire history of Homo sapiens from caveman to soccer mom was a blip in the history of spiders.

I was death on eight legs.

It was a beetle. That's what I was chasing. A big old beetle, much larger than I was.

Larger and slower. He grew in my distorted field of vision. He grew and grew and I powered on.

I wish I could explain why I kept on with the hunt. Sometimes the animal brain takes over for a while and sort of overwhelms the human mind. But that's not what was happening to me. I wasn't overwhelmed. I was just into it.

A last burst of speed! My front legs touched the beetle. He dodged left, but too slow.

I clambered right up on his back.

I positioned my jaws with their deadly fangs, and - "Marco. What are you doing?"

It was Ax. I scampered down off the beetle, feeling like I'd been caught doing something wrong. The beetle ran on, relieved to have escaped. If beetles can feel relief.

"Nothing. I was just letting the spider be a spider." It was a pretty good answer, I thought. "I guess its instincts kind of carried me away."

"Marco, I morphed the identical spider." Ax said.

I felt a wave of guilt and shame suddenly swell up inside me. "Ax, it was just a cockroach. Who cares? Come on, we have a job to do."

"Sometimes humans worry me." Ax said.

I didn't ask him what he meant.

Why had I gotten so into the hunt? Why hadn't I resisted the urge? I flashed on the rage I'd felt when I talked to Tom. Was that it? "I think it's this way." Ax said. He took the lead and I saw him moving in front of me, a spider scurrying effortlessly on his eight legs.

I fell in behind him. I was calm now. The incredible, insane rush of the chase was over. Now the spider was just a tool I was using.

Suddenly, from the sky . . . something fell toward me! It landed right between Ax and me. A grasshopper, three, four times our size. It looked like an elephant.

Then . . . thwap! It fired its huge hind legs and shot into the air. It disappeared as quickly as it had arrived.