NEVER UNDERESTIMATE THE POWER of chitchat. Last winter I found myself in the company of a chatty cabby in beautiful Monterey, Calif. In answer to one of his questions, I mentioned my work with amateur scientists. "Oh," he said, "you must be a monarch man." When I assured him that I had no idea what he meant, our cab took an abrupt turn. "Bear with me," he said as we darted across the parking lot of a small shopping center.

He drove up an alley, onto a main thoroughfare, then took one quick turn again and made a sudden stop. "There," he said, pointing out a well-aged eucalyptus tree. I was puzzled until I saw what had appeared to be a falling leaf flutter back toward its perch. I pulled out my trusty binoculars and carefully scrutinized the branches. There were hundreds, if not thousands, of monarch butterflies nestled in the tree waiting for the rising sun to warm them. "It gets pretty busy by midafternoon," my new friend informed me. I've been a monarch enthusiast ever since.

Danaus plexippus is just an ordinary butterfly in South America, but harsh winters have chiseled the North American variety into one of the most remarkable animals on this continent. Here the monarch is the only insect to migrate both north and south every year, just as birds do. From late August through October, millions head south from as far north as Canada. Those that travel west of the Rocky Mountains overwinter along the Pacific Coast, from Los Angeles to Monterey. The vagabonds on the eastern route roost in just 10 small patches of fir trees in the mountains of central Mexico. Some butterflies travel 4,000 kilometers (2,500 miles) to reach their winter roosts--quite an impressive feat for an insect that tips the scale at barely half a gram.

What is more, no individual lives long enough to complete the migration. The winter survivors mate on the return leg, and, for butterflies, sex is far more lethal than the rigors of a cross-country trek. So these rugged travelers quickly die. Their progeny continue their parents' journey, but many of them also mate, lay eggs and die along the way. Indeed, it takes from three to five generations of butterflies to bring the migratory cycle full circle.

Scientists do not understand why the monarchs of South America do not migrate at all--or, for that matter, why their cousins in Australia (where they are an introduced species) do. And they know little about how the monarchs of North America manage their yearly odyssey. How, for instance, do they sense when to leave their summer homes up north? What factors turn off their reproductive instincts on their southern sojourns but make them sexy on the return passage? And, having never before visited their winter roosts, how do they ever find their way? No one knows.

These deep mysteries can be plumbed with inexpensive apparatus and a little determination, making this field ripe for amateur work. July's column described how to catch and rear butterflies. Here I complete my exposition of sciences lepidopterous by describing some professionally based research in which your entire family can get involved.

The largest of these efforts is called Monarch Watch; it is run by the University of Kansas at Lawrence. Scarcely five years old, the organization already boasts 1,500 paid members and has a program for schools that reaches another 100,000 students and teachers. These numerous amateurs are able to generate many more observations than professionals could collect on their own.

Most volunteers for Monarch Watch take part in its tagging program. These people capture tens of thousands of butterflies and mark each with a small paper tag on the underside of one hind wing. The tags identify when and where the butterfly was first netted. Of the 90,000 insects tagged so far, only 137 have been recaptured. Yet those catches, along with some earlier efforts at tagging these butterflies, have revealed surprising facts about the migration of monarchs. For one, there does not seem to be a single route. Some monarchs make a beeline for Mexico, whereas others actually head southeast and fly toward the Carolinas. Are these insects lost? Do they fly out to sea and die, or do they follow the coast and ultimately make it to Mexico? With more taggers, Monarch Watch may be able to find out.

Monarch Watch is also exploring the possibility of tracking butterflies using various kinds of natural chemical tags that are indicative of the insects' home turf. This year a limited number of volunteers will raise larvae on native milkweed watered by local rainwater. These amateurs will then return the mature butterflies to the University of Kansas for analysis. The researchers hope to identify a chemical signature that will betray a butterfly's point of origin. Then, by sampling the migrating insects at different locations, they should be able to determine the precise routes of migration. Last year volunteers raised the necessary broods in 86 different locales. By this year's end, the organizers of this effort hope to cover all of North America east of the Rocky Mountains.

Maybe then more secrets of butterfly navigation will yield to scientific scrutiny. The observers at Monarch Watch have already discovered one of the ways these long-ranging insects guide themselves. First, they divided a captured brood of migrants into two cages. Using electric lights to mimic the daylight hours, the researchers "time-delayed" one group by shifting the light cycle to start six hours after dawn. They left the daily cycle of the other group unchanged to serve as a control. After spending two weeks conditioning the insects, the experimenters released the butterflies on several sunny afternoons and recorded their direction of flight.

The best route toward the winter roosting sites was just west of due south. In the morning, that direction is well west of the sun's position; in the afternoon, it is east of the sun. The control butterflies knew it was afternoon and correctly headed toward their destination. But the time-delayed monarchs thought it was morning, and they flew toward the northwest, far to the west of the sun's position. This result clearly demonstrates that monarchs are able to find their way, at least in part, by synchronizing their internal clocks with the sun's position.

Yet this ability cannot be the whole story. After all, monarchs seem perfectly capable of navigating even under overcast skies. The butterflies may be following the earth's magnetic field or contours in the land. The answers are waiting for some clever scientist--professional or amateur--to discover.

You can extend the techniques described in July's column to rear monarchs for your own experiments. The folks at Monarch Watch keep up to 150 adults at a time in a space about one meter on a side. To duplicate their success, first connect 12 wooden slats to form a one-meter cube. Cover the top with a hard, clear plastic sheet. Next, staple a one-meter square of fine-mesh plastic window screen one third of the way down the front face and, for easy access to the interior, secure the rest of the square to the wood with Velcro strips. Finally, staple fine-mesh screen over the four remaining surfaces.

You'll need to control light and temperature. Full-spectrum lights are a must. The researchers at Monarch Watch place 10 G.E. daylight fluorescent bulbs 15 centimeters above each of their cages. Use a timer to turn the lights on and off in alternating two-hour intervals starting at 6:30 A.M. with lights-out for the night at 10:30 P.M. This makes for a choppy 16 hours of daytime, but the many dark respites inspire good feeding and mating. Keep the temperature between 23 and 27 degrees Celsius (74 and 80 degrees Fahrenheit). Feed the butterflies solutions of 20 percent sugar water seasoned with a pinch of bee pollen (available at your local health food store) to supply necessary amino acids.

A plastic pot scrubber placed in a shallow dish of the sugar solution makes a dandy fake flower from which the butterflies can feed. Change the solution and sterilize the scrubber every day (or, for a feeding solution that never goes bad, see the instructions on Monarch Watch's World Wide Web site).

In the wild, monarchs lay their eggs only on milkweed plants. In captivity, they still prefer this plant, but green paper can serve as artificial milkweed if the butterflies sense it has carbohydrates that could sustain their young. So if you don't have immediate access to milkweed, try collecting the eggs by hanging inside the cage strips of green blotting paper that have been soaked in sugar water with pollen and allowed to dry. But you'll need to rear the larvae on milkweed. (See July's column for general tips on raising caterpillars.) If you cannot collect these plants locally, Monarch Watch can provide you with seeds. Indeed, if you reside in the East or the Midwest, Monarch Watch can supply you with butterfly larvae, too. And after you raise them to maturity, you can enlist them in Monarch Watch's experiments or test your own theories of how these charming insects behave.

If you would like to get involved in their research and live east of the Rocky Mountains, send $10 to Monarch Watch, University of Kansas, Department of Entomology, Haworth Hall, Lawrence, KS 66045-2106, or call them (toll free) at 1-888-TAGGING. For more information about this project, check out the Monarch Watch World Wide Web site. People west of the Rockies should contact the Monarch Program, P.O. Box 178671, San Diego, CA 92177 (e-mail: Monarchprg@aol.com).

For information about other activities for amateur scientists, contact the Society for Amateur Scientists, 5600, Post Road, #114-341, East Greenwich, RI 02818 or call 1-401-823-7800.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.