MAMMOTH LAKES, Calif. -- The signs of conspicuous consumption already have begun to appear amid the soaring pines that push up from the volcanic soil outside this ski resort in the peaks of the Sierra Nevada.
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Here and there, the odd Jeffrey pine in the Inyo National Forest stands out in contrast to surrounding trees. Its normally lush branches, which can be laden with as much as six years' growth, look unusually ratty.
Look closely and the culprit will come into focus: a caterpillar as fat and long as an adult's pinkie finger, gnawing away at a succulent green needle. Countless others feast nearby.
"There's one, and there's one, and there's one," U.S. Forest Service forester Scott Kusumoto said as he pointed out the insects, rapid-fire, to a visitor.
The caterpillars, the larval stage of the Pandora moth, represent a burgeoning outbreak that's as natural as it is dramatic. By midsummer, experts forecast, millions and millions of the caterpillars will have stripped large tracts of pine trees of their needles.
The last outbreak in the area lasted from 1978 to 1982 and sparked an outcry by those concerned it could wreak permanent damage.
It was a treat, however, for local Indians who have long eaten the larva.
"It was sort of a mix between a fascinating natural history phenomenon and a bad horror movie," said Leslie Dawson, who moved to the area just as the caterpillar population peaked in 1981.
This time around, the defoliation -- mostly harmless and largely temporary -- will be clearly visible to travelers on Highway 395 northeast of the Mammoth Lakes resort area and otherworldly Mono Lake.
Already, early starters among the chubby, striped caterpillars are at work diligently chewing their way, tip to base, through green needles. Each embraces its meal in a tight, leggy grasp as it chomps. Soon, with warmer weather, the presence of the caterpillars should grow audible to anyone who ventures into the forest.
Because there are so many of them, "you can hear their droppings," said Raymond Andrews, a member of a local Paiute Indian tribe that regards the Pandora moth larva as a tasty and nutritious gift from nature.
In 1924, entomologist George P. Englehardt likened the steady fall of caterpillar feces to a sleet storm. During outbreaks, the ground and trees can be so thick with the 3-inch caterpillars that the landscape appears to shudder with their movement, Andrews said.
Forest Service officials estimate the outbreak will affect as many as 40,000 acres of forest, most of it Jeffrey pine. The caterpillars also feed on lodgepole, ponderosa, Coulter and sugar pines.
About one-quarter of that area should be heavily defoliated by midsummer, the rest moderately or lightly so.
"They can completely strip a tree and then crawl down the trunk or drop to the ground and find another tree," said U.S. Forest Service entomologist John Wenz.
A single cache of Pandora moth eggs can hatch dozens of caterpillars. And one of those plump caterpillars can, in turn, eat dozens of needles a day.
Rarely does that sort of voracious feeding kill a tree, although it can leave pines already weakened by drought or disease susceptible to other insects, including devastating bark beetles.
Typically, only about 1 percent of caterpillar-afflicted pines die in an outbreak. The majority should appear no more than heavily pruned.
In recent weeks, the Forest Service has begun a stepped-up public information campaign to forestall any demands to control the outbreak. The agency plans to let it run its course.
"There's no indication it will cause any unacceptable damage," Wenz said.
The caterpillars eat needles but skip buds, allowing pines to sprout new needles in late summer. That regrowth usually comes after the insects finish feeding -- a respite that lets the trees quickly resume photosynthesizing.
The caterpillars also emerge every other year, giving trees in off years a shot at bouncing back.
Comparisons are likely between the Pandora moth and the Brood X cicadas currently emerging on the East Coast after a 17-year hiatus. But outbreaks of Pandora moth don't follow such a clockwork schedule. Nor is it known why the episodic explosions occur.
The Pandora is among the largest species of moth, with wings that can span 4.5 inches. It is native to the West but usually maintains a low profile during its two-year life cycle.
Every 27 years on average, Pandora moth numbers spike. The localized outbreaks typically last four to eight years. The current outbreak is thought to have started in 2001.
In heavy years, caterpillars can carpet the forest. In 1981, many ended up as roadkill on Highway 395, which runs through the forest.
Bill Cox, a 35-year resident of nearby Crowley, remembers having to gingerly pedal his bicycle on the slicked roadway during the last outbreak.
"It felt like it was going to get a little greasy -- like you might have to be careful on the corners," Cox said.
This year, the Forest Service contacted the California Department of Transportation to sweep the highway or post warning signs if the pavement gets too slippery, Wenz said.
The current California outbreak could last another cycle or two before the Pandora population wanes. Other spikes have been recorded in locations across the West over the past century. In southeastern Oregon, an outbreak has been ongoing since 1988.
Hungry squirrels, birds and humans are all enemies of the caterpillar. Its arch nemesis is a virus that poses no risk to humans but can collapse a population in weeks.
"When it crashes, it really crashes," said Nancy Peterson Walter, a Mammoth Lakes ethnologist. LIFE SPAN The Pandora moth is native to the West and usually maintains a low profile during its two-year life cycle.
During the first year, adult moths mate and lay their eggs during a summertime frenzy that lasts just five to 10 days for each insect. The eggs hatch soon after, and the young caterpillars feed into the fall then hibernate. In the spring, they resume feeding in earnest.
By August, they burrow into the loose, pumice-rich soil to pupate for 12 months.
The second year, they re-emerge as moths and begin the two-year cycle anew.
This year is a caterpillar year; 2005 will be a moth year.
Every 27 years on average, the number of Pandora moths spike. Localized outbreaks typically last four to eight years.