Hamden - Even before entering the Magicicada Preserve, an enveloping hum vibrated out onto the road, and within a few steps along the main trail, visitors were bathed in an endless chord that amplified when the sun emerged from the clouds.

"Isn't it amazing?" asked Lawrence Gall, an entomologist at the Peabody Museum of Natural History, as he led the way through the preserve on Wednesday. "It's a low thrumming, throbbing sort of sound."

Providing this unique acoustical experience were some 1 million pinky-sized, winged musicians clustered on low branches, trunks and treetops throughout the hardwood forest - the periodical cicadas that had only days ago emerged from 17 years in solitary underground burrows to begin three weeks of mass choruses of mating calls followed by copulation, egg-laying and death. The sound comes from twin white timbrel structures on the underside of the males.

"I think of their sound as like a huge flock of pigeons on caffeine, all cooing," said Danny Brass of New Haven, a retired veterinarian and amateur entomologist who accompanied Gall and two others from the Peabody.

This was Gall's 12th trip this spring to the 90-acre preserve, owned by the South Central Connecticut Water Co., and one of dozens of visits over the last few weeks by Peabody Museum staff monitoring the emergence of the cicadas.

Unique in the insect world, the cicadas live underground as nymphs for 17 years. Then, when the soil warms to just the right temperature, they dig their way to the surface to shed their skins and transform into adults with neon orange eyes and large, orange-striped wings.

During the walk Wednesday, clusters of mostly females could be seen hanging vertically, horizontally and upside-down on sapling branches - most of the males stayed high in the tree canopy. Others walked slowly up tree trunks or fluttered awkwardly to another perch. A few cicadas landed on shoulders and legs, usually ending up in the palm of one of the visitors' hands for a closer look before being placed back on a branch.

"The ground here is actually spongy, because there are so many emerging here," said Gall, toeing the hole-speckled earth below a large maple tree that hosted a dozen or so cicadas on its trunk. "This is one of the denser colonies in the state."

Colonies have been emerging along the East Coast for the past several weeks but only began emerging at the end of May in Connecticut, the northernmost extent of their range. In the preserve, Gall said, the phenomenon began about a week ago and kicked into full gear in the last day or so.

"This is the first time we've seen mating pairs here," said Gall, as he and Brass hovered around a male and female latched together but facing opposite directions on a tree trunk. The female faced skyward, climbing up the tree as the male faced the ground but moved with its mate.

"This one is literally walking backwards," Brass observed.

Gail Ridge, entomologist with the Connecticut Agricultural Experiment Station, said her office has been getting four to five calls per hour since the emergence began.

"They're in two categories," she said. "People ask, 'How can I kill them?' and 'Where can I go to find them?'"

The cicadas, found only in the south-central part of the state along traprock and basalt ridges, are harmless, Ridge said, and she strongly dissuades people from using pesticides against them. Plus, she said, they'll only be out for another week to 10 days before they'll disappear for another 17 years. As to the second question, she's directing people to Sleeping Giant State Park in Hamden and Hubbard Park in Meriden, but also noted that large colonies are being seen in North Branford and Southington.

"Once people learn about them, they're really quite fascinated by their remarkable life cycle," she said.

A special exhibit on the cicadas at the Peabody has been attracting a lot of interest, Gall said, as have the guided cicada hikes the museum is offering. During Wednesday's visit, Gall and Nicole Palffy-Muhoray, graduate entomologist at the Peabody, collected several specimens, including newly emerged nymphs that had not yet shed their skins, to join about 25 other live ones on display.

"This one just hatched out in the last hour," said Palffy-Muhoray, pointing to a tan bug atop some dead leaves, a pale shadow of the striking winged adult it was about to become. "His wings are still all curled up."

Later on the walk, Gall pointed out a cicada clinging to a tree, half-in and half-out out of its nymphal shell. Its partially exposed adult body was a ghostly white that would darken to black in a few hours. The ground below was littered with empty nymphal shells.

"We're seeing them here at all stages of emergence," he said.

Each of the females, he said, would lay about 600 eggs in tree branches during the three weeks of adulthood, but only a few of those eggs would make it to adulthood. After hatching from the eggs in about 10 days, the nymphs climb out or fall out of the trees and immediately start tunneling their way into their underground chambers.

High mortality rates also afflict the cicadas in their adult stage. Alongside the throngs of live cicadas throughout the preserve were nearly as many who hadn't make it - nymphs who had never gotten out of their shells, adults who had fully emerged except for their wings, which became crumpled in the rain before they had a chance to harden.

Others fell prey to a fungus that shrivels their abdomens. Many others are eaten by birds and other wildlife - just about anything that normally eats insects will feast on periodical cicadas.

"There are all manner of tragedies here," said Palffy-Muhoray, who then stopped to scoop up one of the successful ones.

"Hey buddy, want to be in the exhibit?" she said, dropping the cicada into a collection bowl. "You'll be famous."

j.benson@theday.com