In this modern world of microelectronics and microapartments with "no pets" policies, it was bound to happen. People crave companionship: the patter of tiny feet, the reassuring presence of another being, something to watch scurry about, laugh at, and share space with. So if you can't find companionship, build it.

Already, giant companies like Sony have rushed to meet this need -- but while the AIBO is a cute robo-dog, and its antics are truly amazing, AIBO's price tag of two grand is guaranteed to put it out of the price range of anyone who has to be legitimately concerned with a no pets clause in their lease, like me.

So I found a fun loophole in the system: I built my own pet.

Sparky doesn't look like much -- he's little more than a circuit board on wheels -- but he runs from, or to, light, scurries around my apartment like a kitten on speed, and makes me laugh. I'm in the process of building him a solar-powered brother and have plans for a baby or two in the near future.

Other devotees of mechanical/artificial life have expanded their own spaces into entire cybernetic ecosystems, filling their homes with electronic predators and prey and even sun-tracking robo-sunflowers that provide robot life-forms with life-giving electricity. Eventually, my own little studio could resemble a silicon-and-wire rainforest, with minuscule mechanical beasts roaming a jungle of wires and transistors.

Technically, these little electronic critters fall into two categories: your traditional simple limited-behavior robot that uses store-bought parts, and BEAM (Biology, Electronics, Aesthetics, Mechanics) creatures -- small, smart, simple, and inexpensive machines built from scavenged parts. The father of BEAM robots, Mark Tilden, takes mischievous glee in his ability to assemble robo-stepchildren from the remains of a Walkman. BEAM robots are on the cheap end, running as low as $20, while the fancier non-BEAM machines can run anywhere from $50-300.

My own personal faves come from Craig Maynard, who sells kits of his battery-powered Cybug and the solar-juiced Solarfly. Maynard also deals in add-on kits that can make your little machines stalk each other like electronic cats after digital mice, or feed from another sunflower kit that acts as a robotic food dish.

Be warned, though. These little kits can be tricky to put together. A basic knowledge of soldering and electronics is helpful, but is by no means mandatory. I got along fine with high school shop-class experience and a quick refresher lesson with a soldering iron. After a few hours I had Sparky scuttling around, avoiding obstacles with its little feelers while it sought out the friendly rays of the sun.

But there are even more elaborate techno-critters out there. Sites like Solarbotics, Robohoo, and Robotbooks reveal a frisky subculture of amateur artificial-life companies and aficionados sporting a fascinating array of creatures. Some of the more complex 'bots use "smart" wires that tense and flex when current is applied, and others use built-in computer-programmable circuits that give them shockingly complex behaviors. With each new generation, these little machines act less like gizmos and more like real living creatures. They are well on their way to becoming the best friend a man could ever make.

M. Christian writes and edits fiction and nonfiction. His collection of short stories, Dirty Words, is due out in 2000 from Alyson Books.