Tick, Buzz, It's That Time Again Locusts?

One of the first to spot the invasion in the South was retired Textile Worker Hugh Salmons, who on May 9 saw the glistening bodies on the willow oaks in his front yard in Elkin, N.C. The next morning, Judy Carpenter, 32, of Blairsville, Ga., was in the backyard playing softball with her daughter when she saw the intruder, its red eyes glinting in the sun and its clawed front feet pulling it through the grass. Within 24 hours she had collected 21 of them in a jar from the rhododendron bush in front of the house.

After nearly two decades of a subterranean existence, one of the two largest broods of the 17-year cicadas (pronounced suh-kay-duhs) is back. During the next few weeks and continuing through early July, the Eastern U.S. from Georgia to New York and as far west as Illinois will become infested with these mysterious insects, which emerge from the ground every 17 years to mate and die. This year, as in previous appearances, their numbers are likely to reach into the millions to the acre. The greatest concentrations are expected in the suburbs of Baltimore, Washington, Philadelphia and Cincinnati, where the days will be filled with a cacophony of ticks and buzzes that will wax and wane with the heat of the sun. A population in full song can exceed 100 decibels, roughly the level of a circular buzz saw at full throttle.

Many people still call the cicadas "locusts," because that is what the Pilgrims first called them, thinking no doubt of the locust plagues described in the Old Testament. Actually, those biblical insects were migratory grasshoppers, which even today cause extensive crop damage in Africa, Asia and South America. In contrast, the 17-year cicadas are reasonably harmless bugs whose only sins are sucking sap out of trees for nourishment and killing small branches by laying eggs in them. They also mess up lawns with their 2-in.-long bodies. Vulnerable sapling oaks and fruit trees can easily be protected with a covering of cheesecloth. "They're more of a nuisance than anything else," says Douglass Miller, an entomologist with the Agricultural Research Service in Beltsville, Md. "They do less damage than a good pruning."

Compared with the average bug, which goes from birth to death in less than a year, the 17-year cicada is Methuselah: it has the longest life cycle of any known insect. In all, there are twelve distinct broods of 17-year cicadas, each of which emerges in a different year. This year's group is referred to by scientists as Brood 10. The other large group, Brood 14, is due to make its next appearance in 1991.

What triggers the insect's emergence from the ground exactly on cue in the final months of its life cycle is one of nature's continuing mysteries. Scientists assume that hormones play a role. The creatures also appear at about the time the soil temperature reaches 68 degrees F to 70 degrees F, which is why they are first seen in the South. Says University of Michigan Biologist Thomas Moore: "It's an amazing demonstration of biological complexity."

In its long sojourn underground, subsisting on sap in tree rootlets, the cicada nymph passes through five growth stages, or instars, each of which ends with the insect throwing off its carapace. About two months before it is ready to emerge, the nymph tunnels its way upward, lying at the surface and building a protective earthen turret if the ground is too damp. This final rest stop is truly character building: it apparently enables the insect to develop adult claws and flight muscles to help it cope with life aboveground. "Their bodies undergo a major transformation, especially of muscle structure," says Miller.

As a safeguard against predators, the cicadas usually first crawl out of the ground after sunset. Their main defense, though, may be sheer numbers: birds, raccoons and skunks can crunch up only so many insects. After climbing the nearest vertical object -- a tree or post, for example -- the insects take their last step toward adulthood. They hook their needle-like claws into the surface, arch their backs to break their skin and then wiggle free. A day later they are ready to fly away. All of this is merely a prelude to courtship, with the male cicadas seeking to attract mates with their staccato siren song, produced by vigorously vibrating two drumlike appendages on the abdomen.

The final hours of the cicada's three-week life aboveground are played out as the female deposits hundreds of eggs in a series of pockets cut in twigs. Nine weeks later the microscopic nymphs hatch, drop to the ground and burrow down as far as 2 ft., where they grow, eat and await their coming-out 17 years hence. The fact that this brood will not reappear until 2004 is one reason scientists are reluctant to put too much of their time into unlocking the cicada's secrets. As Richard Froeschner, a research entomologist at the Smithsonian Institution, points out, "Enthusiasm and curiosity tend to wane between generations."